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Trophic Index and Efficiency☆
Trophic Index and Efficiency☆ Timur Pavluk, Russian Research Institute for Integrated Water Management and Protection, Ekaterinburg, Russia Abraham bij de Vaate, Waterfauna Hydrobiological Consultancy, Lelystad, The Netherlands r 2017 Elsevier B.V. All rights reserved.
Introduction This article describes the common scientific meanings of the widely used “trophic index” in classifications in the field of monitoring and assessment. The term “trophic” does not have a distinct application in ecology and is generally used in the description of mean processes like feeding, nourishment, production potential, and food web. The word “trophy” originates from the Greek word trophē which means nourishment or pertaining to nutrition or connected with a source of nutrition. Many other ecological terms are derivatives of the initial word “trophy”: for example, trophic level, trophic niche, trophic guild, trophic net, trophic structure, trophic status, and trophic index. In order to classify a plant or animal community or to assess its quality status, for example, as a result of anthropogenic disturbance, trophic indices were developed. They are mostly applied in aquatic communities since aquatic ecosystems are relatively stable in space and time. Two groups of trophic indices can be distinguished. The first one, the group of trophic status indices, focuses on the primary production potential. In the aquatic environment four types of trophic statuses of the waterbody can be distinguished: the oligotrophic, mesotrophic, eutrophic, and dystrophic status. The second group includes those indices that reflect the complexity of trophic relations between organisms. These indices have been commonly used in bioassessment of the aquatic ecosystem health in general—especially, those systems that have been severely altered as result of anthropogenic activities (e.g., water pollution, physical disturbances). Results of assessments are commonly ranged into quality classes. In the forthcoming sections main types of trophic indices are discussed, mostly used in assessment procedures to evaluate the ecological status of a defined biotope.
Trophic Status Indices TRIX Index This index represents the linear combination of the logarithm of four state variables: TRIX ¼ ðLog10 ½ChA þ aD%O þ minN þ TP þ k Þ=m where ChA is the chlorophyll-a concentration ðmg L1 Þ, aD%O is the dissolved oxygen concentration as absolute percentage deviation from saturation ( ¼ 100%), minN is the mineral nitrogen, dissolved inorganic nitrogen ðsum of Nnitrate þ Nnitrite þ Nammonia in mg L1 Þ, and TP is total phosphorus (mg L1). The coefficients k ¼ 1.5 and m ¼ 1.2 are scale coefficients, introduced to obtain results on a 0–10 scale. TRIX results are arranged in four classes according to Table 1. The index characterizes succinctly the trophic levels in coastal marine areas and was adopted for this purpose by the Italian national legislation. Values exceeding 6 TRIX units are typical for highly productive coastal waters, where eutrophication effects determine frequency of anoxia episodes in the water layer above the bottom. Values lower than 4 TRIX units are associated with scarcely productive coastal waters, while values lower than 3 are usually found in the open sea. Because of the log transformation of the four variables used, annual distributions of TRIX data over homogeneous coastal zones follow or are nearly equal to a Gauss curve.
Carlson's Trophic State Index Transparency of surface waters is often related to the amount of plant nutrients in the water. The more the nutrients, the more the phytoplankton, and as a result the less transparent the water is. Measuring transparency is a common but indirect way to estimate roughly the trophic condition of a waterbody. This condition, called the extent of eutrophication, is a natural aging process of lakes, which is unnaturally accelerated by too many nutrients. Trophic state determination is an important aspect of lake surveys. Trophic state is not the same as water quality, but is one aspect of it. The concept of trophic status is based on the fact that changes in nutrient levels (measured as total phosphorus) cause changes in algal biomass (measured as chlorophyll a) which in turn cause changes in lake clarity (measured as Secchi disk transparency). The trophic state index (TSI) is a convenient way to quantify this relationship. TSI is calculated independently from Secchi disk depth, chlorophyll a, and total phosphorus concentration. It should be taken into account that TSI was ☆
Change History: March 2017. T Pavluk updated Marine Trophic Index section, References and Relevant Websites.
Encyclopedia of Ecology, 2nd edition, Volume 1
doi:10.1016/B978-0-12-409548-9.00608-4
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Table 1
Categories of TRIX classes
TRIX value
Trophic category
o4 4–5 5–6 6–10
Low trophic level Middle trophic level High trophic level Very high trophic level
Adapted from Moncheva, S., Doncheva, V., 2000. Eutrophication index ((E) TRIX)—an operational tool for the Black Sea coastal water ecological quality assessment and monitoring. International Symposium “The Black Sea Ecological Problems” Odessa: SCSEIO, pp. 178–185.
Table 2
Classes of TSI values and their ecological attributes.
TSI
Chl (mg L1)
SD (m) TP (mg L1)
Ecological attributes
o30 30–40 40–50 50–60 60–70 70–80
o0.95 0.95–2.6 2.6–7.3 7.3–20 20–56 56–155
48 8–4 4–2 2–1 0.5–1 0.25–0.5
o6 6–12 12–24 24–48 48–96 96–192
480
4155
o0.25
192–384
Oligotrophy: Clear water, oxygen throughout the year in the entire hypolimnion Hypolimnia of shallower lakes may become anoxic Mesotrophy: Water moderately clear; increasing probability of hypolimnetic anoxia during summer Eutrophy: Anoxic hypolimnia, macrophyte problems possible Blue-green algae dominate, algal scums and macrophyte problems Hypereutrophy (light-limited productivity): Dense algae and macrophytes, algal blooms possible throughout summer Algal scums, few macrophytes
Adapted from Carlson, R.E., Simpson, J., 1996. A coordinator's guide to volunteer lake monitoring methods. USA: North American Lake Management Society Madison.
developed for use with lakes that have few rooted aquatic plants and little nonalgal turbidity. The formulas for calculating the TSI are presented below: TSI ðSDÞ ¼ 60 2 14:41 Ln Secchi disk depthðmetersÞ TSI ðChlÞ ¼ 9:81 Ln chlorophyll aðmg L1 Þ þ 30:6 TSI ðTPÞ ¼ 14:42 Ln total phosphorus ðmg L1 Þ þ 4:15 Each of these three variables can theoretically be used to classify a waterbody, because they are interrelated by linear regression. It is supposed that seasonal average values of variables are used for TSI calculation. If the three TSI values are not similar to each other, it is likely that algal growth may be light- or nitrogen-limited instead of P-limited, or that Secchi disk transparency is affected by erosional silt particles rather than by algae, or something else. One considers that average TSI is a good indicator of water trophic status in general. Average TSI ¼ ðTSIðTPÞ þ TSIðChlÞ þ TSIðSDÞÞ=3 and the values reflect ecological attributes that could be expected in temperate lakes (Table 2).
Trophic Diatom Indices Diatoms are widely recognized and used as indicators of river and stream water quality, including trophic state conditions. The diatom trophic indices describe diatom distribution in relationship to either “dissolved” (Borthophosphate) or “total” phosphorus, that are mostly closely correlated with the nitrogen concentration in the water. Therefore, these indices are treated as broad indicators of the trophic status of water bodies. Three trophic indices based on ecological properties of diatoms were developed in the 1990s: 1. The trophic diatom index (UK TDI), which is used in the United Kingdom. This index was developed by Kelly and Whitton (1995), later on revised by Kelly et al. in 2001. 2. The TDI developed by Coring et al. (1999), which is used in Germany (German TDI). 3. The TDI developed by Rott et al. (1999), which is used in Austria (Austrian TDI). All these indices were designed for use in rivers, which means that they are not applicable in lakes and other stagnant water bodies. Calculation of the indices is based on the weighted average of the equation of Zelenka and Marvan for each diatom species. Two values are assigned to the species: a value reflecting the tolerance or affinity to a certain water quality (good or bad) and a value that indicates how strong (or weak) this relationship is. In addition, the index values are weighted by the relative abundance of the diatom in the sample (percentage of a particular diatom species in the sample):
Conservation Ecology: Trophic Index and Efficiency Xn j¼1
Index ¼ Xn
497
aj sj vj
j¼1
aj vj
where aj is the abundance or proportion of species j in samples, sj is the pollution sensitivity of species j (optimum), and vj is the indicator value (tolerance). Sensitivity value (s) is divided into five classes and varies from 1 (highly sensitive to phosphorous) to 5 (highly tolerant to phosphorous). Tolerance value (v) ranges from 1 (taxa with a broad distribution) to 3 (taxa that are restricted to a narrow range of nutrient conditions). All TDIs mentioned are very similar in principal and differ in the number of species used and in the values of s and v which have been attributed to the species after compiling the data from literature and from ordinations. Also the number of the trophic classes distinguished may vary.
Benthic Trophic State Index The ratio of gross production to respiration (P:R), measured quantitatively by oxygen flux rates, has long been used to characterize the trophic status of aquatic ecosystems. A ratio of 1.0 indicates a balance of photoautotrophic and heterotrophic processes, ratios o1.0 indicate heterotrophic dominance of processes, and ratios 41.0 indicate photoautotrophically dominated communities. The benthic TSI is based on relative rates of sediment–water oxygen exchange in opaque (dark) and transparent (light) chambers incubated at or near ambient temperature. The benthic TSI (BTSI) uses data from short-term metabolic measurements not as a quantitative measure of shoal community P:R, a continuous variable, but to assign a categorical value that broadly reflects the extent to which that environment supports the ecological processes associated with benthic autotrophy. The BTSI, expressed in the values 0, 1, 2, or 3, is assigned to shallow sediments based on the relative magnitude of hourly rates of maximum net community production (NCPmax) and respiration (CR). In calculating the BTSI, negative values are assigned to all oxygen fluxes into the sediment. When the BTSI increases, so does the degree of autotrophy, and thus the contribution to support grazing organisms, hypoxia reduction, nutrient sequestration, and biotic stability of the sediment. Ranges of gross production/respiration (P:R) associated with each BTSI value are shown in Table 3 including examples of rates representative of each BTSI value (condition) and corresponding net community production at light saturation (NCPmax) and community respiration (CR). Ranges of gross production/respiration (P:R) associated with each BTSI value are given including examples of rates representative of each BTSI value (condition) and corresponding net community production at light saturation (NCPmax) and community respiration (CR), both in mg O2 m2 h1. Negative values indicate fluxes from water to sediments. NA, not applicable. The BTSI is a method to assess the functioning of shallow benthic ecosystems. It is methodologically relatively simple assessment method and reflects established ecological processes as the result of anthropogenic pressure. The BTSI relates potential benthic photoautotrophy to benthic respiration through discrete classification rather than the commonly used continuous variable of P:R ratio.
Oligochaete Trophic Index The association of oligochaetes with organic enrichment of water was used to develop the “oligochaete trophic index.” The index is based on the oligochaete community structure, where species were assigned to categories depending on their preference for, or tolerance of, oligotrophic, mesotrophic, or eutrophic conditions. A number of modifications of the oligochaete trophic index have been developed since 1977. A modification index used in the Great Lakes (North America) is calculated as X X X X 1=2 n0 þ n1 þ 2 n2 þ 3 n3 X X X X c n0 þ n1 þ n2 þ n3 where n0, n1, n2, and n3 are the total numbers of individuals belonging to each of the four ecological groups. Species characteristic Table 3
Classification of shallow sediments by the BTSI.
BTSI
P:R
Condition
NCPmax
CR
Sediment classification
0 1 2 3
NA 40–0.5 0.5–1.0 41.0
NCPmaxrCR CRoNCPmaxr0 0oNCPmaxr|CR| |CP|oNCPmax
25 10 2 50
25 25 25 25
Totally heterotrophic Net heterotrophic Net autotrophic Highly autotrophic
Adapted from Rizzo, W.M., Berry, B.E., Wetzel, R.L., et al., 1996. A metabolism-based trophic index for comparing the ecological values of shallow-water sediment habitats. Estuaries 19, 247–256, with permission from estuarine Research Federation.
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for oligotrophic waters are assigned to group 0, those for mesotrophic waters to group 1, those for eutrophic waters to group 2, and those for hypertrophic waters (Limnodrillus hoffmeisteri and Tubifex tubifex) comprise group 3. The coefficient c depends upon the total oligochaete number per square meter as outlined as follows: c ¼ 1, n43600; c ¼ 3/4, 1200ono3600; c ¼ 1/2, 400ono1200; c ¼ 1/4, 130ono400; c ¼ 0, 0ono130. Index values between 0.6 and 1.0 indicate mesotrophic conditions, while higher and lower values indicate eutrophic and oligotrophic conditions, respectively. In general, when the index was applied to the Great Lakes, it appeared that the values give a reasonable evaluation of trophic conditions. Most sites in the upper lakes fall into the oligotrophic category, with areas of known higher productivity (near shore northern Lake Michigan; Saginaw Bay, Lake Huron) exhibit higher index values. Sites in Lake Erie generally fall into the mesotrophic range, while in Lake Ontario near shore sites were classified as mesotrophic, and offshore sites are oligotrophic.
Trophic Level Index The trophic level index (TLI) is an indicator of lake water quality. Four parameters are combined to construct the TLI: concentrations of total nitrogen, total phosphorus, and chlorophyll a, and transparency. These parameters reflect the dynamics of the annual lake cycle. Nitrogen and phosphorus are essential plant nutrients. High levels of water-bound nitrogen and phosphorus most often come from agricultural runoff and urban wastewater, but can also come from geothermal inputs and deep springs that leach phosphorus from the rock geology. Chlorophyll a is a good indicator of the total quantity of algae in a lake. Algae are a natural part of any lake system, but large amounts of algae decrease water clarity, make the water look green, can form surface scums, reduce dissolved oxygen levels, can alter pH levels, and can produce unpleasant tastes and smells. Transparency of the water is measured using a Secchi disk. Calculation of the TLI:
• • • • •
TLnitrogen ¼ 3.61 þ 3.01 log (Ntotal) TLphosphorus ¼ 0.218 þ 2.92 log (Ptotal) TLtransparency ¼ 5.10 þ 2.27 log (1/Secchi disk depth 1/40) TLchlorophyl ¼ 2.22 þ 2.54 log (Chl a) TLI¼ (TLnitrogen þ TLphosphorus þ TLtransparency þ TLchlorophyl)/4
The higher the TLI, the worse the water quality. Trophic level ranges are grouped into trophic states for quantitative description as shown in Table 4. Trophic states, as determined by the four key variables: 1. 2. 3. 4. 5.
Microtrophic lakes are very clean, and often have snow or glacial sources. Oligotrophic lakes are clear and blue, with low levels of nutrients and algae. Mesotrophic lakes have moderate levels of nutrients and algae. Eutrophic lakes are green and murky, with higher amounts of nutrients and algae. Supertrophic lakes are fertile and saturated in phosphorus and nitrogen, and have very high algae growth and blooms during calm sunny periods. 6. Hypertrophic lakes are highly fertile and supersaturated in phosphorus and nitrogen. They are rarely suitable for recreation, and habitat for desirable aquatic species is limited. Table 4
Trophic state and corresponding quantitative parameters of the trophic level index
Trophic state
Nutrient enrichment category
TLI
Chl a (mg m3)
Secchi disk depth (m)
Tphosphorus (mg m3)
Tnitrogen (mg m3)
Ultramicrotrophic Microtrophic Oligotrophic Mesotrophic Eutrophic Surpertrophic Hypertrophic
Practically pure Very low Low Medium High Very high Saturated
0.0–1.0 1.0–2.0 2.0–3.0 3.0–4.0 4.0–5.0 5.0–6.0 46.0
o0.33 0.33–0.82 0.82–2.0 2–5 5–12 12–31 431
425 25–15 15–7 7.0–2.8 2.8–1.1 1.1–0.4 o0.4
o1.8 1.8–4.1 4.1–9.0 9–20 20–43 43–96 496
o34 34–73 73–157 157–337 337–725 725–1558 41558
Adapted from Environment Bay of Plenty, Tropic Level Index, http://www.ebop.govt.nz/Water/Lakes/Trophic-Level-Index.asp, with permission.
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Trophic Index of Macrophytes The trophic index of macrophytes (TIM) is a tool for indicating the trophic state of running waters. Concentrations of soluble reactive phosphorus in both the water body and sediment pore water were assigned to macrophyte species and related to their phosphorus demand. The TIM is calculated with Zelenka and Marvan's formula for the determination of the saprobic index: n X
TIM ¼
IV a W a Qa
i¼1 n X
W a Qa
i¼1
where IVa is the indicator value for species a, depending on the assigned trophic category, Wa is the weighting factor for the tolerance of species a, and Q a is the quantity of species a in the river section. TIM values were classified into trophic categories to indicate the trophic status of the river sections examined (Table 5).
Trophic Relation Indices Infaunal Trophic Index The infaunal trophic index (ITI) was developed to identify changed and degraded environmental conditions as a result of organic pollution in coastal waters. The approach is based on the allocation of macroinvertebrate species to one of four groups based on the type of food consumed by the species and where the food was obtained from. The ITI and its response to organic pollution is based on the principle that with increasing organic enrichment the dominant feeding type changes from those species which feed at the interface of the sediment and water, such as suspension feeders (which occur in areas of low organic enrichment), through to species which are predominantly deposit feeders (in areas of high organic enrichment). After determining the abundance of taxa belonging to each of next four feeding groups, (1) detrital feeders, (2) interface detrital feeders, (3) deposit feeders, and (4) specialized feeders, the ITI is calculated by combining these groups in the following formula: ITI ¼ 100 33:33
ð0n1 þ 1n2 þ 2n3 þ 3n4 Þ ðn1 þ n2 þ n3 þ n4 Þ
where n1–4 are the numbers of individuals in feeding groups 1–4 distinguished, and 0–3 are factors in the numerator (scaling factors). Values of the index range from 0 to 100 with low values indicating degraded conditions. With the ITI seabed areas are classified into either “normal” (values 100–60), “changed” (60–30), or “degraded” (30–0). The ITI has been tested widely in fully marine conditions and showed most statistically powerful results. However, due to the natural prevalence of deposit feeders in estuaries and the generally lower number of taxa, the ITI can act in an aberrant way in transient areas and is therefore not a useful indicator for estuaries. The index has a direct link to eutrophication indicators.
Marine Trophic Index Differences in the trophic level of selected groups of species provide a reliable indicator of the integrity of an ecosystem. The marine trophic index indicates changes in the mean trophic level of fish communities regionally and globally. Trophic level is Table 5 categories
Classification of TIM values into trophic
TIM value
Trophic state
1.00–1.44 1.45–1.86 1.87–2.24 2.25–2.62 2.63–3.04 3.05–3.49 3.50–4.00
Oligotrophic Oligomesotrophic Mesotrophic Mesoeutrophic Eutrophic Eupolytrophic Polytrophic
Adapted from Schneider, S., Melzer, A., 2003. The trophic index of macrophytes (TIM)—a new tool for indicating the trophic state of running waters. International Review of Hydrobiology 88, 49–67, with permission from WileyVCH, STM.
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defined as the position of an organism in the food chain and ranges from a value of 1 for primary producers to 5 for marine mammals and humans. The method to determine the trophic level of a consumer is to add one level to the mean trophic level of its prey. The equation corresponding to a species trophic level calculation is X TLi ¼ TLj DCij j
where TLj is the fractional trophic level of the prey j, and DCij is the fraction of j in the diet of species i. Thus defined, the trophic level of most fishes and other aquatic consumers can have any value between 2.0 and 5.0. Trophic level changes through the life history of fish, with juveniles having lower trophic levels than adults. Existent annual fishery database supplies sufficient information for marine trophic index computing. Therefore, mean trophic level for year k may be found as P ðTLi Þ ðY ik Þ TLk ¼ i X Y ik i
where Yi is the landing (catch) of species (group) i, and TLi is the trophic level of species (group) i. Trophic level estimates for fish, based on their diet composition, can be found in FishBase, the global online database for fish, and for invertebrates in the Sea-Around-Us database. The marine trophic index is a powerful indicator of marine ecosystem integrity and sustainability of fisheries at the global and regional levels. Whether a fishery is balanced from ecological point of view we may define with a “Fisheries in Balance” index (FIB) (Pauly et al., 2000). Since biomass transfer efficiencies between trophic levels are only about 10%, it follows that the rate of biological production is much greater at lower than it is at higher trophic levels. Fisheries catches, at least to begin with, will tend to increase as the trophic level declines. At this point the fisheries will target species lower in the food web. The FIB index is defined, for any year i, by TLi ! TLo ! 1 1 log Yo∗ FIB ¼ log Yi∗ TE TE where Yi is the catch at year i, TLi is the mean trophic level of the catch at year i, Yo is the catch, TLo the mean trophic level of the catch at the start (o refers to any year used as a baseline) of the series being analyzed, and TE is the transfer efficiency of biomass or energy between trophic levels. The FIB index is stable (zero) over periods of time when changes in trophic levels are matched by appropriate changes in the catch in the opposite direction. The index increases if both catches and mean trophic level increase for any reason, for example higher fish biomass, or geographic expansion, suggesting that the fishery was expanding to stocks previously not, or lightly exploited. Decreases may be observed when TL shows stepwise decline by a corresponding increase in catches.
Index of Trophic Completeness The index of trophic completeness (ITC) is based on communities of freshwater macroinvertebrates. Species were divided into 12 trophic groups on the basis of their trophic characteristics(Table 6). Each trophic group fulfills a function in the benthic community. The Table 6 database
Characteristics of the macroinvertebrate groups distinguished in the ITC, including the relative number of taxa per group present in the
Trophic group, no.
Diet
Feeding behavior
Food size (mm)
Relative number (%)
1 2 3 4 5 6 7 8 9 10 11 12
Carnivory Carnivory Omnivory Herbivory Herbivory Herbivory Herbivory Herbivory Carnivory Carnivory Herbivory Omnivory
Active shredder/chewer Passive shredder/chewer Shredder/chewer/collector Shredder/chewer Shredder/chewer Scraper Collector Filtrator Sucker (incomplete food ingestion) Sucker (total food ingestion) Sucker Shredder/chewer
41 41 41 41 o1 o1 o1 o1 41 41 41 o1
9.8 3.6 5.9 7.8 2.6 26.3 22.7 8.7 6.6 2.4 1.9 1.7
Adapted from Pavluk, T. I., bij de Vaate, A. and Leslie, H. A. (2000). Development of an index of trophic completeness for benthic macroinvertebrate communities in flowing waters. Hydrobiologia 427, 135–141.
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Table 7 Indicative value (weight factor) and respective score of the trophic groups. Trophic group
C (weight factor)
Ln C (Ci)
1 2 3 4 5 6 7 8 9 10 11 12
10.2 27.6 16.9 12.8 39.2 3.8 4.4 11.5 15.2 41.4 53.2 57.3
2.3 3.3 2.8 2.6 3.7 1.3 1.5 2.4 2.7 3.7 4.0 4.1
Adapted from bij de Vaate, A., Pavluk, T. I. (2004). Practicability of the index of trophic completeness for running waters. Hydrobiologia 519, 49–60.
Table 8 classes.
Quality class score for the ITC with five
Quality class
Ctot
Quality description
I II III IV V
Z28 21–28 14–21 7–14 0–7
High Good Moderate Poor Bad
Adapted from bij de Vaate, A., Pavluk, T.I. (2004). Practicability of the index of trophic completeness for running waters. Hydrobiologia 519, 49–60.
trophic characteristics of each group include the following criteria: plant/animal ratio in the diet, feeding mechanism, food size, food acquisition behavior, and energy and substance transfer ways. Any undisturbed benthic macroinvertebrate community should be represented by members of each of these 12 trophic groups, irrespective of the part of the river studied and its geographical region. The ITC was developed to show the degree of benthic community functional completeness reflected via its trophic relations to other components of an aquatic ecosystem. The modern modification of the ITC calculation presumes application of weight factor (Table 7), because the probability to meet species of different trophic groups in the aquatic community is unequal and quality of water and number of trophic groups present has no straight linear relationship. The ITC is calculated using the formula Ctot ¼
n X
Ci
i¼1
where Ctot is the total score for the index, n is the number of trophic groups present in the data set, and Ci is the Ln-transformed indicative value of trophic group i. The relation between the ITC value and the quality classes is given in Table 8 for an assessment system with five quality classes. The index indicates the functionality of the community and is based on the assumption that in healthy environment all trophic groups will be present. Natural fluctuations (e.g., floods, drought, ice covering) may influence the community structure, but their long-term effects do not result in the extinction of trophic groups. Recently a handy tool for the ITC calculation for macroinvertebrates was developed. It is called MaTroS (Macrozoobenthos Trophic Structure). The tool has a friendly interface with a simple algorithm for the index calculation (http://www.macro.nemiekb.ru/).
Summary Applied research of aquatic ecosystems involves enormous amount of parameters to give a detailed description of ecological processes and to verify the degree of anthropogenic interference that takes place. To transform parameters studied into a clear and
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integrated form indices are used of which the group of trophic indices is the most popular. Two groups of the indices are distinguished: trophic indices based on the primary production potential of ecosystems, and the indices based on the structure of energy and substance transferring between trophic levels of aquatic inhabitants. Trophic indices allow one to make comparative studies between very different aquatic ecosystems, even those that are located in different continents with completely different species compositions.
See also: Ecological Data Analysis and Modelling: Climate Change Models; Climate Change Models. Ecological Processes: Physical Transport Processes in Ecology: Advection, Diffusion, and Dispersion. General Ecology: Ecological Efficiency
References Coring, E., Schneider, S., Hamm, A., Hofmann, G., 1999. Durchgehendes Trophiesystem auf der Grundlage der Trophieindikaation mit Kieselalgen. Germany: Deutscher Verband für Wasserwirtschaft und Kulturbau e.V Koblenz. Kelly, M.G., Whitton, B.A., 1995. The trophic diatom index: a new index for monitoring eutrophication in rivers. Journal of Applied Phycology 7, 433–444. Pauly, D., Christensen, V., Walters, C., 2000. Ecopath, Ecosim, and Ecospace as tools for evaluating ecosystem impact of fisheries. ICES Journal of Marine Science 57 (3), 697–706. Rott, E., Pipp, E., Pfister, P., et al., 1999. Indikationslisten für aufwuchsalgen in österreichischen fliessgewässern. Teil 2: Trophieindikation. Wien, Austria: Bundesministerium für Land- und Forstwirtschaft.
Further Reading bij de Vaate, A., Pavluk, T., 2004. Practicability of the index of trophic completeness for running waters. Hydrobiologia 519, 49–60. Burns, N.M., Rutherford, J.C., Clayton, J.S., 1999. A monitoring and classification system for New Zealand lakes and reservoirs. Journal of Lakes Research and Management 15, 255–271. Carlson, R.E., 1977. A trophic state index for lakes. Limnology and Oceanography 22, 361–369. Carlson, R.E., Simpson, J., 1996. A coordinator's guide to volunteer lake monitoring methods. USA: North American Lake Management Society Madison. Giovanardi, F., Vollenweider, R.A., 2004. Trophic conditions of marine coastal waters: experience in applying the trophic index TRIX to two areas of the Adriatic and Tyrrhenian seas. Journal of Limnology 63, 199–218. Howmiller, R.P., Scott, M.A., 1977. An environmental index based on relative abundance of oligochaete species. Journal of the Water Pollution Control Federation 49, 809–815. Milbrink, G., 1983. An improved environmental index based on the relative abundance of oligochaete species. Hydrobiologia 102, 89–97. Moncheva, S., Doncheva, V., 2000. Eutrophication index ((E) TRIX)—an operational tool for the Black Sea coastal water ecological quality assessment and monitoring. International Symposium “The Black Sea Ecological Problems”Odessa: SCSEIO, pp. 178–185. Pauly, D., Watson, R., 2005. Background and interpretation of the ‘marine trophic index’ as a measure of biodiversity. Philosophical Transactions of the Royal Society B 360, 415–423. Pavluk, T.I., bij de Vaate, A., Leslie, H.A., 2000. Development of an index of trophic completeness for benthic macroinvertebrate communities in flowing waters. Hydrobiologia 427, 135–141. Rizzo, W.M., Berry, B.E., Wetzel, R.L., et al., 1996. A metabolism-based trophic index for comparing the ecological values of shallow-water sediment habitats. Estuaries 19, 247–256. Schneider, S., Melzer, A., 2003. The trophic index of macrophytes (TIM)—a new tool for indicating the trophic state of running waters. International Review of Hydrobiology 88, 49–67. Word, J.Q. (1978). The infaunal trophic index Southern California Coastal Water Research Project, Annual Report. El Segundo, California. pp. 19–39. Word, J.Q. (1980). Classification of benthic invertebrates into infaunal trophic index feeding groups Southern California Coastal Water Research Project, Biennial Report 1979–1980. Long Beach California, pp. 103–121. Word, J.Q. (1990). The infaunal trophic index, a functional approach to benthic community analyses. University of Washington Seattle, Washington, PhD Thesis.
Relevant Websites http://www.fishbase.net—FishBase. http://www.NALMS.org—North American Lake Management Society (NALMS). http://www.seaaroundus.org—Sea-Around-U.S. database; Web Products: Information by Species. http://www.epa.gov—U.S. Environmental Protection Agency, External Links Disclaimer. http://www.macro.nemi-ekb.ru—Macrozoobenthos Trophic Structure (MaTroS).
Introduction This article describes the common scientific meanings of the widely used “trophic index” in classifications in the field of monitoring and assessment. The term “trophic” does not have a distinct application in ecology and is generally used in the description of mean processes like feeding, nourishment, production potential, and food web. The word “trophy” originates from the Greek word trophē which means nourishment or pertaining to nutrition or connected with a source of nutrition. Many other ecological terms are derivatives of the initial word “trophy”: for example, trophic level, trophic niche, trophic guild, trophic net, trophic structure, trophic status, and trophic index. In order to classify a plant or animal community or to assess its quality status, for example, as a result of anthropogenic disturbance, trophic indices were developed. They are mostly applied in aquatic communities since aquatic ecosystems are relatively stable in space and time. Two groups of trophic indices can be distinguished. The first one, the group of trophic status indices, focuses on the primary production potential. In the aquatic environment four types of trophic statuses of the waterbody can be distinguished: the oligotrophic, mesotrophic, eutrophic, and dystrophic status. The second group includes those indices that reflect the complexity of trophic relations between organisms. These indices have been commonly used in bioassessment of the aquatic ecosystem health in general—especially, those systems that have been severely altered as result of anthropogenic activities (e.g., water pollution, physical disturbances). Results of assessments are commonly ranged into quality classes. In the forthcoming sections main types of trophic indices are discussed, mostly used in assessment procedures to evaluate the ecological status of a defined biotope.
Trophic Status Indices TRIX Index This index represents the linear combination of the logarithm of four state variables: TRIX ¼ ðLog10 ½ChA þ aD%O þ minN þ TP þ k Þ=m where ChA is the chlorophyll-a concentration ðmg L1 Þ, aD%O is the dissolved oxygen concentration as absolute percentage deviation from saturation ( ¼ 100%), minN is the mineral nitrogen, dissolved inorganic nitrogen ðsum of Nnitrate þ Nnitrite þ Nammonia in mg L1 Þ, and TP is total phosphorus (mg L1). The coefficients k ¼ 1.5 and m ¼ 1.2 are scale coefficients, introduced to obtain results on a 0–10 scale. TRIX results are arranged in four classes according to Table 1. The index characterizes succinctly the trophic levels in coastal marine areas and was adopted for this purpose by the Italian national legislation. Values exceeding 6 TRIX units are typical for highly productive coastal waters, where eutrophication effects determine frequency of anoxia episodes in the water layer above the bottom. Values lower than 4 TRIX units are associated with scarcely productive coastal waters, while values lower than 3 are usually found in the open sea. Because of the log transformation of the four variables used, annual distributions of TRIX data over homogeneous coastal zones follow or are nearly equal to a Gauss curve.
Carlson's Trophic State Index Transparency of surface waters is often related to the amount of plant nutrients in the water. The more the nutrients, the more the phytoplankton, and as a result the less transparent the water is. Measuring transparency is a common but indirect way to estimate roughly the trophic condition of a waterbody. This condition, called the extent of eutrophication, is a natural aging process of lakes, which is unnaturally accelerated by too many nutrients. Trophic state determination is an important aspect of lake surveys. Trophic state is not the same as water quality, but is one aspect of it. The concept of trophic status is based on the fact that changes in nutrient levels (measured as total phosphorus) cause changes in algal biomass (measured as chlorophyll a) which in turn cause changes in lake clarity (measured as Secchi disk transparency). The trophic state index (TSI) is a convenient way to quantify this relationship. TSI is calculated independently from Secchi disk depth, chlorophyll a, and total phosphorus concentration. It should be taken into account that TSI was ☆
Change History: March 2017. T Pavluk updated Marine Trophic Index section, References and Relevant Websites.
Encyclopedia of Ecology, 2nd edition, Volume 1
doi:10.1016/B978-0-12-409548-9.00608-4
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Table 1
Categories of TRIX classes
TRIX value
Trophic category
o4 4–5 5–6 6–10
Low trophic level Middle trophic level High trophic level Very high trophic level
Adapted from Moncheva, S., Doncheva, V., 2000. Eutrophication index ((E) TRIX)—an operational tool for the Black Sea coastal water ecological quality assessment and monitoring. International Symposium “The Black Sea Ecological Problems” Odessa: SCSEIO, pp. 178–185.
Table 2
Classes of TSI values and their ecological attributes.
TSI
Chl (mg L1)
SD (m) TP (mg L1)
Ecological attributes
o30 30–40 40–50 50–60 60–70 70–80
o0.95 0.95–2.6 2.6–7.3 7.3–20 20–56 56–155
48 8–4 4–2 2–1 0.5–1 0.25–0.5
o6 6–12 12–24 24–48 48–96 96–192
480
4155
o0.25
192–384
Oligotrophy: Clear water, oxygen throughout the year in the entire hypolimnion Hypolimnia of shallower lakes may become anoxic Mesotrophy: Water moderately clear; increasing probability of hypolimnetic anoxia during summer Eutrophy: Anoxic hypolimnia, macrophyte problems possible Blue-green algae dominate, algal scums and macrophyte problems Hypereutrophy (light-limited productivity): Dense algae and macrophytes, algal blooms possible throughout summer Algal scums, few macrophytes
Adapted from Carlson, R.E., Simpson, J., 1996. A coordinator's guide to volunteer lake monitoring methods. USA: North American Lake Management Society Madison.
developed for use with lakes that have few rooted aquatic plants and little nonalgal turbidity. The formulas for calculating the TSI are presented below: TSI ðSDÞ ¼ 60 2 14:41 Ln Secchi disk depthðmetersÞ TSI ðChlÞ ¼ 9:81 Ln chlorophyll aðmg L1 Þ þ 30:6 TSI ðTPÞ ¼ 14:42 Ln total phosphorus ðmg L1 Þ þ 4:15 Each of these three variables can theoretically be used to classify a waterbody, because they are interrelated by linear regression. It is supposed that seasonal average values of variables are used for TSI calculation. If the three TSI values are not similar to each other, it is likely that algal growth may be light- or nitrogen-limited instead of P-limited, or that Secchi disk transparency is affected by erosional silt particles rather than by algae, or something else. One considers that average TSI is a good indicator of water trophic status in general. Average TSI ¼ ðTSIðTPÞ þ TSIðChlÞ þ TSIðSDÞÞ=3 and the values reflect ecological attributes that could be expected in temperate lakes (Table 2).
Trophic Diatom Indices Diatoms are widely recognized and used as indicators of river and stream water quality, including trophic state conditions. The diatom trophic indices describe diatom distribution in relationship to either “dissolved” (Borthophosphate) or “total” phosphorus, that are mostly closely correlated with the nitrogen concentration in the water. Therefore, these indices are treated as broad indicators of the trophic status of water bodies. Three trophic indices based on ecological properties of diatoms were developed in the 1990s: 1. The trophic diatom index (UK TDI), which is used in the United Kingdom. This index was developed by Kelly and Whitton (1995), later on revised by Kelly et al. in 2001. 2. The TDI developed by Coring et al. (1999), which is used in Germany (German TDI). 3. The TDI developed by Rott et al. (1999), which is used in Austria (Austrian TDI). All these indices were designed for use in rivers, which means that they are not applicable in lakes and other stagnant water bodies. Calculation of the indices is based on the weighted average of the equation of Zelenka and Marvan for each diatom species. Two values are assigned to the species: a value reflecting the tolerance or affinity to a certain water quality (good or bad) and a value that indicates how strong (or weak) this relationship is. In addition, the index values are weighted by the relative abundance of the diatom in the sample (percentage of a particular diatom species in the sample):
Conservation Ecology: Trophic Index and Efficiency Xn j¼1
Index ¼ Xn
497
aj sj vj
j¼1
aj vj
where aj is the abundance or proportion of species j in samples, sj is the pollution sensitivity of species j (optimum), and vj is the indicator value (tolerance). Sensitivity value (s) is divided into five classes and varies from 1 (highly sensitive to phosphorous) to 5 (highly tolerant to phosphorous). Tolerance value (v) ranges from 1 (taxa with a broad distribution) to 3 (taxa that are restricted to a narrow range of nutrient conditions). All TDIs mentioned are very similar in principal and differ in the number of species used and in the values of s and v which have been attributed to the species after compiling the data from literature and from ordinations. Also the number of the trophic classes distinguished may vary.
Benthic Trophic State Index The ratio of gross production to respiration (P:R), measured quantitatively by oxygen flux rates, has long been used to characterize the trophic status of aquatic ecosystems. A ratio of 1.0 indicates a balance of photoautotrophic and heterotrophic processes, ratios o1.0 indicate heterotrophic dominance of processes, and ratios 41.0 indicate photoautotrophically dominated communities. The benthic TSI is based on relative rates of sediment–water oxygen exchange in opaque (dark) and transparent (light) chambers incubated at or near ambient temperature. The benthic TSI (BTSI) uses data from short-term metabolic measurements not as a quantitative measure of shoal community P:R, a continuous variable, but to assign a categorical value that broadly reflects the extent to which that environment supports the ecological processes associated with benthic autotrophy. The BTSI, expressed in the values 0, 1, 2, or 3, is assigned to shallow sediments based on the relative magnitude of hourly rates of maximum net community production (NCPmax) and respiration (CR). In calculating the BTSI, negative values are assigned to all oxygen fluxes into the sediment. When the BTSI increases, so does the degree of autotrophy, and thus the contribution to support grazing organisms, hypoxia reduction, nutrient sequestration, and biotic stability of the sediment. Ranges of gross production/respiration (P:R) associated with each BTSI value are shown in Table 3 including examples of rates representative of each BTSI value (condition) and corresponding net community production at light saturation (NCPmax) and community respiration (CR). Ranges of gross production/respiration (P:R) associated with each BTSI value are given including examples of rates representative of each BTSI value (condition) and corresponding net community production at light saturation (NCPmax) and community respiration (CR), both in mg O2 m2 h1. Negative values indicate fluxes from water to sediments. NA, not applicable. The BTSI is a method to assess the functioning of shallow benthic ecosystems. It is methodologically relatively simple assessment method and reflects established ecological processes as the result of anthropogenic pressure. The BTSI relates potential benthic photoautotrophy to benthic respiration through discrete classification rather than the commonly used continuous variable of P:R ratio.
Oligochaete Trophic Index The association of oligochaetes with organic enrichment of water was used to develop the “oligochaete trophic index.” The index is based on the oligochaete community structure, where species were assigned to categories depending on their preference for, or tolerance of, oligotrophic, mesotrophic, or eutrophic conditions. A number of modifications of the oligochaete trophic index have been developed since 1977. A modification index used in the Great Lakes (North America) is calculated as X X X X 1=2 n0 þ n1 þ 2 n2 þ 3 n3 X X X X c n0 þ n1 þ n2 þ n3 where n0, n1, n2, and n3 are the total numbers of individuals belonging to each of the four ecological groups. Species characteristic Table 3
Classification of shallow sediments by the BTSI.
BTSI
P:R
Condition
NCPmax
CR
Sediment classification
0 1 2 3
NA 40–0.5 0.5–1.0 41.0
NCPmaxrCR CRoNCPmaxr0 0oNCPmaxr|CR| |CP|oNCPmax
25 10 2 50
25 25 25 25
Totally heterotrophic Net heterotrophic Net autotrophic Highly autotrophic
Adapted from Rizzo, W.M., Berry, B.E., Wetzel, R.L., et al., 1996. A metabolism-based trophic index for comparing the ecological values of shallow-water sediment habitats. Estuaries 19, 247–256, with permission from estuarine Research Federation.
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for oligotrophic waters are assigned to group 0, those for mesotrophic waters to group 1, those for eutrophic waters to group 2, and those for hypertrophic waters (Limnodrillus hoffmeisteri and Tubifex tubifex) comprise group 3. The coefficient c depends upon the total oligochaete number per square meter as outlined as follows: c ¼ 1, n43600; c ¼ 3/4, 1200ono3600; c ¼ 1/2, 400ono1200; c ¼ 1/4, 130ono400; c ¼ 0, 0ono130. Index values between 0.6 and 1.0 indicate mesotrophic conditions, while higher and lower values indicate eutrophic and oligotrophic conditions, respectively. In general, when the index was applied to the Great Lakes, it appeared that the values give a reasonable evaluation of trophic conditions. Most sites in the upper lakes fall into the oligotrophic category, with areas of known higher productivity (near shore northern Lake Michigan; Saginaw Bay, Lake Huron) exhibit higher index values. Sites in Lake Erie generally fall into the mesotrophic range, while in Lake Ontario near shore sites were classified as mesotrophic, and offshore sites are oligotrophic.
Trophic Level Index The trophic level index (TLI) is an indicator of lake water quality. Four parameters are combined to construct the TLI: concentrations of total nitrogen, total phosphorus, and chlorophyll a, and transparency. These parameters reflect the dynamics of the annual lake cycle. Nitrogen and phosphorus are essential plant nutrients. High levels of water-bound nitrogen and phosphorus most often come from agricultural runoff and urban wastewater, but can also come from geothermal inputs and deep springs that leach phosphorus from the rock geology. Chlorophyll a is a good indicator of the total quantity of algae in a lake. Algae are a natural part of any lake system, but large amounts of algae decrease water clarity, make the water look green, can form surface scums, reduce dissolved oxygen levels, can alter pH levels, and can produce unpleasant tastes and smells. Transparency of the water is measured using a Secchi disk. Calculation of the TLI:
• • • • •
TLnitrogen ¼ 3.61 þ 3.01 log (Ntotal) TLphosphorus ¼ 0.218 þ 2.92 log (Ptotal) TLtransparency ¼ 5.10 þ 2.27 log (1/Secchi disk depth 1/40) TLchlorophyl ¼ 2.22 þ 2.54 log (Chl a) TLI¼ (TLnitrogen þ TLphosphorus þ TLtransparency þ TLchlorophyl)/4
The higher the TLI, the worse the water quality. Trophic level ranges are grouped into trophic states for quantitative description as shown in Table 4. Trophic states, as determined by the four key variables: 1. 2. 3. 4. 5.
Microtrophic lakes are very clean, and often have snow or glacial sources. Oligotrophic lakes are clear and blue, with low levels of nutrients and algae. Mesotrophic lakes have moderate levels of nutrients and algae. Eutrophic lakes are green and murky, with higher amounts of nutrients and algae. Supertrophic lakes are fertile and saturated in phosphorus and nitrogen, and have very high algae growth and blooms during calm sunny periods. 6. Hypertrophic lakes are highly fertile and supersaturated in phosphorus and nitrogen. They are rarely suitable for recreation, and habitat for desirable aquatic species is limited. Table 4
Trophic state and corresponding quantitative parameters of the trophic level index
Trophic state
Nutrient enrichment category
TLI
Chl a (mg m3)
Secchi disk depth (m)
Tphosphorus (mg m3)
Tnitrogen (mg m3)
Ultramicrotrophic Microtrophic Oligotrophic Mesotrophic Eutrophic Surpertrophic Hypertrophic
Practically pure Very low Low Medium High Very high Saturated
0.0–1.0 1.0–2.0 2.0–3.0 3.0–4.0 4.0–5.0 5.0–6.0 46.0
o0.33 0.33–0.82 0.82–2.0 2–5 5–12 12–31 431
425 25–15 15–7 7.0–2.8 2.8–1.1 1.1–0.4 o0.4
o1.8 1.8–4.1 4.1–9.0 9–20 20–43 43–96 496
o34 34–73 73–157 157–337 337–725 725–1558 41558
Adapted from Environment Bay of Plenty, Tropic Level Index, http://www.ebop.govt.nz/Water/Lakes/Trophic-Level-Index.asp, with permission.
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Trophic Index of Macrophytes The trophic index of macrophytes (TIM) is a tool for indicating the trophic state of running waters. Concentrations of soluble reactive phosphorus in both the water body and sediment pore water were assigned to macrophyte species and related to their phosphorus demand. The TIM is calculated with Zelenka and Marvan's formula for the determination of the saprobic index: n X
TIM ¼
IV a W a Qa
i¼1 n X
W a Qa
i¼1
where IVa is the indicator value for species a, depending on the assigned trophic category, Wa is the weighting factor for the tolerance of species a, and Q a is the quantity of species a in the river section. TIM values were classified into trophic categories to indicate the trophic status of the river sections examined (Table 5).
Trophic Relation Indices Infaunal Trophic Index The infaunal trophic index (ITI) was developed to identify changed and degraded environmental conditions as a result of organic pollution in coastal waters. The approach is based on the allocation of macroinvertebrate species to one of four groups based on the type of food consumed by the species and where the food was obtained from. The ITI and its response to organic pollution is based on the principle that with increasing organic enrichment the dominant feeding type changes from those species which feed at the interface of the sediment and water, such as suspension feeders (which occur in areas of low organic enrichment), through to species which are predominantly deposit feeders (in areas of high organic enrichment). After determining the abundance of taxa belonging to each of next four feeding groups, (1) detrital feeders, (2) interface detrital feeders, (3) deposit feeders, and (4) specialized feeders, the ITI is calculated by combining these groups in the following formula: ITI ¼ 100 33:33
ð0n1 þ 1n2 þ 2n3 þ 3n4 Þ ðn1 þ n2 þ n3 þ n4 Þ
where n1–4 are the numbers of individuals in feeding groups 1–4 distinguished, and 0–3 are factors in the numerator (scaling factors). Values of the index range from 0 to 100 with low values indicating degraded conditions. With the ITI seabed areas are classified into either “normal” (values 100–60), “changed” (60–30), or “degraded” (30–0). The ITI has been tested widely in fully marine conditions and showed most statistically powerful results. However, due to the natural prevalence of deposit feeders in estuaries and the generally lower number of taxa, the ITI can act in an aberrant way in transient areas and is therefore not a useful indicator for estuaries. The index has a direct link to eutrophication indicators.
Marine Trophic Index Differences in the trophic level of selected groups of species provide a reliable indicator of the integrity of an ecosystem. The marine trophic index indicates changes in the mean trophic level of fish communities regionally and globally. Trophic level is Table 5 categories
Classification of TIM values into trophic
TIM value
Trophic state
1.00–1.44 1.45–1.86 1.87–2.24 2.25–2.62 2.63–3.04 3.05–3.49 3.50–4.00
Oligotrophic Oligomesotrophic Mesotrophic Mesoeutrophic Eutrophic Eupolytrophic Polytrophic
Adapted from Schneider, S., Melzer, A., 2003. The trophic index of macrophytes (TIM)—a new tool for indicating the trophic state of running waters. International Review of Hydrobiology 88, 49–67, with permission from WileyVCH, STM.
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defined as the position of an organism in the food chain and ranges from a value of 1 for primary producers to 5 for marine mammals and humans. The method to determine the trophic level of a consumer is to add one level to the mean trophic level of its prey. The equation corresponding to a species trophic level calculation is X TLi ¼ TLj DCij j
where TLj is the fractional trophic level of the prey j, and DCij is the fraction of j in the diet of species i. Thus defined, the trophic level of most fishes and other aquatic consumers can have any value between 2.0 and 5.0. Trophic level changes through the life history of fish, with juveniles having lower trophic levels than adults. Existent annual fishery database supplies sufficient information for marine trophic index computing. Therefore, mean trophic level for year k may be found as P ðTLi Þ ðY ik Þ TLk ¼ i X Y ik i
where Yi is the landing (catch) of species (group) i, and TLi is the trophic level of species (group) i. Trophic level estimates for fish, based on their diet composition, can be found in FishBase, the global online database for fish, and for invertebrates in the Sea-Around-Us database. The marine trophic index is a powerful indicator of marine ecosystem integrity and sustainability of fisheries at the global and regional levels. Whether a fishery is balanced from ecological point of view we may define with a “Fisheries in Balance” index (FIB) (Pauly et al., 2000). Since biomass transfer efficiencies between trophic levels are only about 10%, it follows that the rate of biological production is much greater at lower than it is at higher trophic levels. Fisheries catches, at least to begin with, will tend to increase as the trophic level declines. At this point the fisheries will target species lower in the food web. The FIB index is defined, for any year i, by TLi ! TLo ! 1 1 log Yo∗ FIB ¼ log Yi∗ TE TE where Yi is the catch at year i, TLi is the mean trophic level of the catch at year i, Yo is the catch, TLo the mean trophic level of the catch at the start (o refers to any year used as a baseline) of the series being analyzed, and TE is the transfer efficiency of biomass or energy between trophic levels. The FIB index is stable (zero) over periods of time when changes in trophic levels are matched by appropriate changes in the catch in the opposite direction. The index increases if both catches and mean trophic level increase for any reason, for example higher fish biomass, or geographic expansion, suggesting that the fishery was expanding to stocks previously not, or lightly exploited. Decreases may be observed when TL shows stepwise decline by a corresponding increase in catches.
Index of Trophic Completeness The index of trophic completeness (ITC) is based on communities of freshwater macroinvertebrates. Species were divided into 12 trophic groups on the basis of their trophic characteristics(Table 6). Each trophic group fulfills a function in the benthic community. The Table 6 database
Characteristics of the macroinvertebrate groups distinguished in the ITC, including the relative number of taxa per group present in the
Trophic group, no.
Diet
Feeding behavior
Food size (mm)
Relative number (%)
1 2 3 4 5 6 7 8 9 10 11 12
Carnivory Carnivory Omnivory Herbivory Herbivory Herbivory Herbivory Herbivory Carnivory Carnivory Herbivory Omnivory
Active shredder/chewer Passive shredder/chewer Shredder/chewer/collector Shredder/chewer Shredder/chewer Scraper Collector Filtrator Sucker (incomplete food ingestion) Sucker (total food ingestion) Sucker Shredder/chewer
41 41 41 41 o1 o1 o1 o1 41 41 41 o1
9.8 3.6 5.9 7.8 2.6 26.3 22.7 8.7 6.6 2.4 1.9 1.7
Adapted from Pavluk, T. I., bij de Vaate, A. and Leslie, H. A. (2000). Development of an index of trophic completeness for benthic macroinvertebrate communities in flowing waters. Hydrobiologia 427, 135–141.
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Table 7 Indicative value (weight factor) and respective score of the trophic groups. Trophic group
C (weight factor)
Ln C (Ci)
1 2 3 4 5 6 7 8 9 10 11 12
10.2 27.6 16.9 12.8 39.2 3.8 4.4 11.5 15.2 41.4 53.2 57.3
2.3 3.3 2.8 2.6 3.7 1.3 1.5 2.4 2.7 3.7 4.0 4.1
Adapted from bij de Vaate, A., Pavluk, T. I. (2004). Practicability of the index of trophic completeness for running waters. Hydrobiologia 519, 49–60.
Table 8 classes.
Quality class score for the ITC with five
Quality class
Ctot
Quality description
I II III IV V
Z28 21–28 14–21 7–14 0–7
High Good Moderate Poor Bad
Adapted from bij de Vaate, A., Pavluk, T.I. (2004). Practicability of the index of trophic completeness for running waters. Hydrobiologia 519, 49–60.
trophic characteristics of each group include the following criteria: plant/animal ratio in the diet, feeding mechanism, food size, food acquisition behavior, and energy and substance transfer ways. Any undisturbed benthic macroinvertebrate community should be represented by members of each of these 12 trophic groups, irrespective of the part of the river studied and its geographical region. The ITC was developed to show the degree of benthic community functional completeness reflected via its trophic relations to other components of an aquatic ecosystem. The modern modification of the ITC calculation presumes application of weight factor (Table 7), because the probability to meet species of different trophic groups in the aquatic community is unequal and quality of water and number of trophic groups present has no straight linear relationship. The ITC is calculated using the formula Ctot ¼
n X
Ci
i¼1
where Ctot is the total score for the index, n is the number of trophic groups present in the data set, and Ci is the Ln-transformed indicative value of trophic group i. The relation between the ITC value and the quality classes is given in Table 8 for an assessment system with five quality classes. The index indicates the functionality of the community and is based on the assumption that in healthy environment all trophic groups will be present. Natural fluctuations (e.g., floods, drought, ice covering) may influence the community structure, but their long-term effects do not result in the extinction of trophic groups. Recently a handy tool for the ITC calculation for macroinvertebrates was developed. It is called MaTroS (Macrozoobenthos Trophic Structure). The tool has a friendly interface with a simple algorithm for the index calculation (http://www.macro.nemiekb.ru/).
Summary Applied research of aquatic ecosystems involves enormous amount of parameters to give a detailed description of ecological processes and to verify the degree of anthropogenic interference that takes place. To transform parameters studied into a clear and
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integrated form indices are used of which the group of trophic indices is the most popular. Two groups of the indices are distinguished: trophic indices based on the primary production potential of ecosystems, and the indices based on the structure of energy and substance transferring between trophic levels of aquatic inhabitants. Trophic indices allow one to make comparative studies between very different aquatic ecosystems, even those that are located in different continents with completely different species compositions.
See also: Ecological Data Analysis and Modelling: Climate Change Models; Climate Change Models. Ecological Processes: Physical Transport Processes in Ecology: Advection, Diffusion, and Dispersion. General Ecology: Ecological Efficiency
References Coring, E., Schneider, S., Hamm, A., Hofmann, G., 1999. Durchgehendes Trophiesystem auf der Grundlage der Trophieindikaation mit Kieselalgen. Germany: Deutscher Verband für Wasserwirtschaft und Kulturbau e.V Koblenz. Kelly, M.G., Whitton, B.A., 1995. The trophic diatom index: a new index for monitoring eutrophication in rivers. Journal of Applied Phycology 7, 433–444. Pauly, D., Christensen, V., Walters, C., 2000. Ecopath, Ecosim, and Ecospace as tools for evaluating ecosystem impact of fisheries. ICES Journal of Marine Science 57 (3), 697–706. Rott, E., Pipp, E., Pfister, P., et al., 1999. Indikationslisten für aufwuchsalgen in österreichischen fliessgewässern. Teil 2: Trophieindikation. Wien, Austria: Bundesministerium für Land- und Forstwirtschaft.
Further Reading bij de Vaate, A., Pavluk, T., 2004. Practicability of the index of trophic completeness for running waters. Hydrobiologia 519, 49–60. Burns, N.M., Rutherford, J.C., Clayton, J.S., 1999. A monitoring and classification system for New Zealand lakes and reservoirs. Journal of Lakes Research and Management 15, 255–271. Carlson, R.E., 1977. A trophic state index for lakes. Limnology and Oceanography 22, 361–369. Carlson, R.E., Simpson, J., 1996. A coordinator's guide to volunteer lake monitoring methods. USA: North American Lake Management Society Madison. Giovanardi, F., Vollenweider, R.A., 2004. Trophic conditions of marine coastal waters: experience in applying the trophic index TRIX to two areas of the Adriatic and Tyrrhenian seas. Journal of Limnology 63, 199–218. Howmiller, R.P., Scott, M.A., 1977. An environmental index based on relative abundance of oligochaete species. Journal of the Water Pollution Control Federation 49, 809–815. Milbrink, G., 1983. An improved environmental index based on the relative abundance of oligochaete species. Hydrobiologia 102, 89–97. Moncheva, S., Doncheva, V., 2000. Eutrophication index ((E) TRIX)—an operational tool for the Black Sea coastal water ecological quality assessment and monitoring. International Symposium “The Black Sea Ecological Problems”Odessa: SCSEIO, pp. 178–185. Pauly, D., Watson, R., 2005. Background and interpretation of the ‘marine trophic index’ as a measure of biodiversity. Philosophical Transactions of the Royal Society B 360, 415–423. Pavluk, T.I., bij de Vaate, A., Leslie, H.A., 2000. Development of an index of trophic completeness for benthic macroinvertebrate communities in flowing waters. Hydrobiologia 427, 135–141. Rizzo, W.M., Berry, B.E., Wetzel, R.L., et al., 1996. A metabolism-based trophic index for comparing the ecological values of shallow-water sediment habitats. Estuaries 19, 247–256. Schneider, S., Melzer, A., 2003. The trophic index of macrophytes (TIM)—a new tool for indicating the trophic state of running waters. International Review of Hydrobiology 88, 49–67. Word, J.Q. (1978). The infaunal trophic index Southern California Coastal Water Research Project, Annual Report. El Segundo, California. pp. 19–39. Word, J.Q. (1980). Classification of benthic invertebrates into infaunal trophic index feeding groups Southern California Coastal Water Research Project, Biennial Report 1979–1980. Long Beach California, pp. 103–121. Word, J.Q. (1990). The infaunal trophic index, a functional approach to benthic community analyses. University of Washington Seattle, Washington, PhD Thesis.
Relevant Websites http://www.fishbase.net—FishBase. http://www.NALMS.org—North American Lake Management Society (NALMS). http://www.seaaroundus.org—Sea-Around-U.S. database; Web Products: Information by Species. http://www.epa.gov—U.S. Environmental Protection Agency, External Links Disclaimer. http://www.macro.nemi-ekb.ru—Macrozoobenthos Trophic Structure (MaTroS).