Growth and nutrient uptake of Gracilaria lemaneiformis under different nutrient conditions with implications for ecosystem services: A case study in the laboratory and in an enclosed mariculture area in the East China Sea

Aquatic Botany 153 (2019) 73–80

Contents lists available at ScienceDirect

Aquatic Botany journal homepage: www.elsevier.com/locate/aquabot

Growth and nutrient uptake of Gracilaria lemaneiformis under different nutrient conditions with implications for ecosystem services: A case study in the laboratory and in an enclosed mariculture area in the East China Sea

T

⁎

Yuanliang Duana, Na Yanga, Ming Hua, Zhangliang Weib, Hongsheng Bic, Yuanzi Huoa,c, , Peimin Hea a b c

College of Marine Ecology and Environment, Shanghai Ocean University, Shanghai 201306, China Key Laboratory of Tropical Marine Bio-Resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science, 146 Williams St., Solomons, MD, 20688, United States

A R T I C LE I N FO

A B S T R A C T

Keywords: Gracilaria Mariculture Nutrient bioextration Integrated multi-trophic aquaculture Ecosystem service

The growth and nutrient uptake of Gracilaria lemaneiformis under different nutrient conditions, with implications for ecosystem services, were evaluated in the laboratory and in an enclosed mariculture sea area in Yantian Bay at the coast of East China Sea. In laboratory experiments, the specific growth rate (SGR) ranged 1.29%/ d–7.99%/d, and nitrogen (N), phosphorus (P), and dissolved inorganic carbon (C) uptake rate was 0.067–1.603 μmol/(g∙h), 0.002–0.069 μmol/(g∙h), and 4.01–31.25 μmol/(g∙h), respectively, under different nutrient conditions. In field experiments, the SGR ranged from 6.30%/d to 13.00%/d, and the average C sequestration rate was 9.25 mg/(g DW·h) and 6.68 mg/(g DW·h) in the G. lemaneiformis cultivation area (region 1) and fish cage area (region 4), respectively. The NH4+-N uptake rate of G. lemaneiformis was the highest in region 1 and region 4 with 56.98 ± 4.81 μg/(g DW·h) and 38.68 ± 7.12 μg/(g DW·h), respectively. The maximum removal efficiency of NH4+-N, NO3−-N, NO2–N, and PO43--P were 45.99–59.79%, 13.10–30.21%, 12.88–14.11%, and 27.07–31.49% in G. lemaneiformis cultivated areas compared with those in fish cage area. The extrapolated results showed that 1192.03 tonnes of C, 128.10 tonnes of N and 15.89 tonnes of P would be simultaneously sequestered from the seawater through G. lemaneiformis cultivation in Yantian Bay. Results indicated that G. lemaneiformis had high growth rates and nutrient removal efficiencies under different nutrient conditions, which made it a good candidate for seaweed/animals integrated multi-trophic aquaculture in nutrient bioextraction and economic diversification.

1. Introduction Mariculture continues to be the fastest growing animal food-producing sector globally (Ottinger et al., 2016; Troell et al., 2017; Liu et al., 2018), with production equaling that of wild fisheries in 2006 (Abreu et al., 2011a). Mariculture provides economic profits and decreases the intensity of exploitation on diminishing wild living resources. With the growth of global demand for aquatic products in recent decades, most countries have already reached their maximum aquaculture capacity (Chen and Qiu, 2014). The rapid expansion of intensive monoculture systems is to meet the demand for fish supplies (Ferreira et al., 2014). However, human activities in coastal areas have placed greater pressure on already over-exploited marine ecosystems (Chopin et al.,

⁎

2001). Excess nutrients derived from traditional marine cage farming enter the marine environment as feces and uneaten feed (Chopin et al., 2001). There were indications that feed inputs of approximately 80–88% of C, 52–95% of N, and 85% of P into marine fish culture systems may be lost to the environment through uneaten feed, fish excretion, and respiration (Skriptsova and Miroshnikova, 2011). These organic and inorganic inputs into fish culture have substantially impacted organic matter and nutrient loading in coastal areas (Zhou et al., 2006), resulting in eutrophication, harmful algal blooms, and anoxia (Wu, 1995; Yang and Fei, 2003; Huo et al., 2011). Intensive mariculture of fish, shrimp, shellfish, and other economic aquatic animals not only results in an increase of nutrient concentrations in coastal areas, but also alters dissolved inorganic nutrient conditions and sedimentary environments (Huo et al., 2012).

Corresponding author at: College of Marine Ecology and Environment, Shanghai Ocean University, Shanghai 201306, China. E-mail address: [email protected] (Y. Huo).

https://doi.org/10.1016/j.aquabot.2018.11.012 Received 12 July 2018; Received in revised form 16 November 2018; Accepted 25 November 2018 Available online 27 November 2018 0304-3770/ © 2018 Elsevier B.V. All rights reserved.

Aquatic Botany 153 (2019) 73–80

Y. Duan et al.

through a CuSO4 solution and acclimated to the culture environment for 1 week before experimentation. The nitrogen (N) concentration in the medium was adjusted to 500 μmol/L, 100 μmol/L, 50 μmol/L, and 5 μmol/L by NaNO3, which were referred to as N1, N2, N3, and N4, respectively. The phosphorus (P) concentration was 30 μmol/L, 15 μmol/L, 5 μmol/L, and 0.5 μmol/L by Na2HPO4, which were referred to as P1, P2, P3 and P4, respectively. A total of 16 combinations of N and P concentrations was arrayed in the present study (Table 1). The inoculation biomass of G. lemaneiformis was set at 0.224 ± 0.01 g; these were cultured in 50-mL colorimetric tubes containing 50 mL experimental medium. All experiments were performed separately in at least triplicate, and aseptic techniques were employed in all experimental steps. The experimental conditions were the same as mentioned above. These experiments lasted 3 days and samples were collected at the beginning and every 12 h until the end of experiment.

There have been numerous investigations into improving seawater quality and reducing nutrient loadings from mariculture (Troell et al., 1999; Yu and Yang, 2008; Huo et al., 2012). Macroalgae have higher photosynthetic efficiencies than terrestrial plants and are more efficient at capturing carbon (C) (Packer, 2009). From the mid-1970s, researchers began to develop methods using macroalgae to treat mariculture system effluents (Fei et al., 1999; Chung et al., 2002; Neori et al., 2004). Macroalgae play an important role in recycling and transforming nutrients in mariculture ecosystems; this is largely due to their capacity to absorb and store nutrients in their tissues (Yang et al., 2006; Marinho-Soriano et al., 2009). Moreover, marine plants have developed C concentrating mechanisms that can generate a high CO2 concentration around rubisco (Moulin et al., 2011). Several macroalgae species have also be shown to have the ability to use HCO3− as a source of C (Klenell et al., 2004). These physiological properties play an important role in slowing global warming and ocean acidification. In addition, macroalgae not only offers an ecologically friendly alternative, but also provides an additional food source for producers (Yang et al., 2006; Marinho-Soriano et al., 2009; Xu and Gao, 2012). Gracilaria is widely distributed globally, but most commonly in tropical and subtropical waters. It is one of most cultivated and valuable seaweeds in the world. In China, more than 30 species of Gracilaria have been recorded to date; the main cultivated species are Gracilaria lemaneiformis, Gracilaria tenuistipitata, and Gracilaria asiatica (Tseng, 2001; Zou et al., 2004; Yang et al., 2006). Gracilaria lemaneiformis naturally grows in the temperature range of 12–23 ℃ (Brawley and Xiugeng, 1988). Some studies have shown that G. lemaneiformis can effectively remove superfluous nutrients from the ocean (Yang et al., 2006; Ye et al., 2006; Zhou et al., 2006; Wang et al., 2007). In order to satisfy agar and feed industrial demand, as well as improving water quality, extensive cultivation of G. lemaneiformis has been encouraged in Chinese coastal areas (Yang and Fei, 2003; Fei, 2004; Yang et al., 2006). At present, most researches on G. lemaneiformis have been focused on the relationship between photosynthesis and C concentration (Zou et al., 2004); changes in physiological characteristics and antioxidative enzyme defense system under high ratios of N to P (Yu and Yang, 2008); growth in situ (Yang et al., 2006); nutrient uptake rate (Abreu et al., 2011b); and its effect on microalgal growth (Wang et al., 2007; Lu et al., 2011). In addition, there have also been some co-cultured experiments on G. lemaneiformis in coastal areas (e. g., in a system cocultured with fish) (Zhou et al., 2006). However, it is still unknown on the physiological performance of G. lemaneiformis under different nutrient conditions, and nutrient removal efficiencies from seawater under high nutrient concentrations. The aim of this study was to determine the growth and nutrient uptake rate (C, N, and P) of G. lemaneiformis cultivated under different nutrient structure conditions, and to evaluate its ecosystem services in an enclosed mariculture sea area in Yantian Bay at the coast of East China Sea. The results of present study would supply fundamental scientific data for further utilizing G. lemaneiformis to nutrient bioextration under different nutrient conditions at coastal areas of throughout world.

2.1.1. Growth rate of G. lemaneiformis The fresh weight of G. lemaneiformis after drying with tissue paper was measured at the beginning of the experiment and every 12 h until the end, and the specific growth rate (SGR, %/d) was calculated according to the following equation:

SGR =

(ln Wi − ln Wi − 1) × 100 t

where the Wi represents the fresh weight collected at time i, Wi-1 represents the fresh weight collected at time i-1, t represents days (d) between i and i-1. 2.1.2. Nutrient uptake rate of G. lemaneiformis under different nutrient conditions Concentrations of NO3−-N and PO43--P were measured according to protocols of the Joint Global Ocean Flux Study (JGOFS, 1994). Dissolved inorganic C (DIC) was determined by the total organic C analysis meter TOC-VCPH (Shimadzu, Japan). Nutrient uptake rates (NUR, μmol/[g∙h]) and nutrient removal efficiencies (NRE, %) of G. lemaneiformis were estimated based on the following equation (Abreu et al., 2011b; Xu and Gao, 2012):

NUR =

(C0 − Ct ) × V W×t

NRE =

(C0 − Ct ) × 100 C0

where the C0 represents the nutrient and DIC concentrations at the beginning (μmol/L), Ct represents the nutrient and DIC concentration at time t (μmol/L), V represents the volume of the culture medium (L), t represents the time interval of sampling (h), and W represents the fresh weight of the G. lemaneiformis cultured in the experiment (g). 2.2. Experiment 2: Ecosystem services of G. lemaneiformis cultivated in an enclosed mariculture sea area in Yantian Bay 2.2.1. Study area The study was conducted at a mariculture base in Yantian Bay (26.72°–26.84 °N, 119.76°–119.83 °E), one of enclosed bays inside Sansha Bay, located on the coast of the East China Sea (Fig. 1). There were five different regions: G. lemaneiformis cultivation area (region 1), G. lemaneiformis cultivation area (region 2), Crassostrea gigas cultured area (region 3), Pseudosciaena crocea cage area (region 4), and a control area (region 5). During the study period, seawater temperature, salinity, and pH were 21.0 ℃ –24.2 ℃, 23–30, and 7.60–8.00, respectively.

2. Materials and methods 2.1. Experiment 1: Growth and nutrient uptake of G. lemaneiformis under different nutrient conditions in the laboratory Gracilaria lemaneiformis was collected from its cultivation area in Yantian Bay in July 2012 (Fig. 1). After debris and epiphytes were removed from the surface using a soft brush and rinsing with sterile seawater, G. lemaneiformis was cultured aseptically in VSE medium in illuminating incubators under a temperature of 20 ± 2 ℃, salinity of 30 ± 0.2, and irradiance of 80 μmol/(m2∙s) with a photoperiod of 12 h light: 12 h dark. G. lemaneiformis was aerated after being filtered

2.2.2. Nutrient uptake efficiency and photosynthetic rates of G. lemaneiformis in Yantian Bay The black and white bottle method was used in this experiment. 74

Aquatic Botany 153 (2019) 73–80

Y. Duan et al.

Fig. 1. Location of the Yantian enclosed sea at the coast of East China Sea. Note: region 1, region 2, region 3, region 4, and region 5 represent G. lemaneiformis cultivation area, G. lemaneiformis cultivation area, Crassostrea gigas cultured area, Pseudosciaena crocea cage area, and control area, respectively. Table 1 Concentrations of nitrogen (N) and phosphorus (P) in 16 different experimental treatments. Combination

NO3−-N (μmol/L)

PO43−-P (μmol/L)

N1P1 N1P2 N1P3 N1P4 N2P1 N2P2 N2P3 N2P4 N3P1 N3P2 N3P3 N3P4 N4P1 N4P2 N4P3 N4P4

500 500 500 500 100 100 100 100 50 50 50 50 5 5 5 5

30 15 5 0.5 30 15 5 0.5 30 15 5 0.5 30 15 5 0.5

R=

(CBC − CBZ ) × V W×t

where CBC represents the concentration of nitrogen and phosphorus in the BC at the end of the experiment (mg/L), CBZ represents the concentration of nitrogen and phosphorus in the BZ at the end of the experiment (mg/L), V represents the volume of bottle (L), W represents the dry weight of G. lemaneiformis (g), and t represents the duration of experiment (h). The C sequestration efficiency (RDIC, mg/[g DW∙h]) of G. lemaneiformis was calculated according to the following equation:

RDIC = RBZ − RBC − RHZ RBZ =

(DIC0 − DICBZ ) × V W×t

RBC =

(DIC0 − DICBC ) × V W×t

RHZ =

(DIC0 − DICHZ ) × V W×t

where RBZ represents the C sequestration efficiency of G. lemaneiformis in the BZ of the experiment (mg/[g DW∙h]), and the same were true for RBC and RHZ; DIC0 represents the concentration of DIC at the beginning of the experiment (mg/L); DICBZ represents the concentration of DIC in BZ at the end of the experiment (mg/L), and the same were true for DICBC and DICHZ; V represents the bottle volume (L), W represents the dry weight of G. lemaneiformis (g), and t represents the duration of the experiment (h). The O2 production efficiency (RDO, mg/[g DW∙h]) of G. lemaneiformis was calculated according to the following equation (Yao et al., 2013):

Samples of G. lemaneiformis 2.50 ± 0.05 g in weight were placed in black and white bottles filled with in situ filtered seawater. The experiment was divided into three groups: white bottle + G. lemaneiformis (BZ), black bottle + G. lemaneiformis (HZ), and the control group of white bottle (BC). These bottles were suspended in region 1 and region 4. The experiment lasted 4 h (10:00 am–2:00 pm) on a sunny day. Nutrients (NH4+-N, NO3−-N, NO2–N, PO43-P, and DIC) and dissolved oxygen (DO) were determined. The nutrient uptake efficiency (R, μg/[g DW∙h]) of G. lemaneiformis was calculated according to the following equation:

RDO = RBZ − RBC − RHZ 75

Aquatic Botany 153 (2019) 73–80

Y. Duan et al.

RBZ =

(DOBZ − DO0) × V W×t

RBC =

(DOBC − DO0) × V W×t

RHZ =

(DOHZ − DO0) × V W×t

respectively). At P concentrations of 15 μmol/L and 5 μmol/L, the N uptake rate increased with N concentration; when the concentration of P was 30 μmol/L and 0.5 μmol/L, the N uptake rate in N2 and N3 groups was higher than those in other groups (P = 0.000–0.047). The N uptake rate of G. lemaneiformis in the P2 and P3 groups was higher than in the P1 group (P = 0.000–0.047). The uptake rates on P of G. lemaneiformis under different nutrient structure conditions are shown in Table 4. When the N concentration was 50 μmol/L, the P uptake rate of G. lemaneiformis was the highest (P = 0.00–0.925). The results of variance analysis showed that changes of P concentrations had a significant effect on the P uptake rate (P = 0.027), while there was no significant effect regarding N concentration (P = 0.138). The N and P uptake rates in N1 and N3 groups at 36 h were higher than those in other groups (P = 0.000–0.035); the P uptake rates in N2 and N3 groups at 60 h was also higher than those in other groups (P = 0.000–0.017). The DIC uptake rate reached up to 10 μmol/(g∙h) in the first 12 h, and then gradually decreased over time, to less than 7 μmol/(g∙h) within 60 h (Table 5). N and P concentration variations had no significant effect on DIC uptake rate (P = 0.068 and P = 0.086, respectively).

where RBZ represents the O2 production efficiency of G. lemaneiformis in the BZ of the experiment (mg/(g DW∙h)), and the same were true for RBC and RHZ; DOBZ represents the concentration of DO in BZ at the end of the experiment (mg/L), and the same were true for DOBC and DOHZ; DO0 represents the concentration of DIC at the beginning of the experiment (mg/L); V represents the bottle volume (L), W represents the dry weight of G. lemaneiformis (g), and t represents the duration of the experiment (h). 2.2.3. Growth and nutrient removal rates of G. lemaneiformis in Yantian Bay Five sampling sites were established in region 1. At each sampling site, wet and dry weights of G. lemaneiformis were measured and recorded. The SGR and maximum photochemical quantum yield (Fv/Fm) were calculated. Fv/Fm was measured by the method described by Lin et al. (2009). The experiment was initiated on 3 Oct, and ended on 8 Nov, in 2013. Surface water samples were collected in the field. Three sampling sites were established in each research region (Fig. 1). Temperature, salinity, pH, and DO were measured directly in the field. The concentrations of chlorophyll a (Chl a), NH4+-N, NO2−-N, NO3−-N, PO43-P, and DIC were measured in the laboratory. The samples were brought back to the laboratory under freezing conditions as soon as possible. The experiment began on 24 Oct, and ended on 8 Nov, in 2013. Samples were collected at the beginning of the experiment and every 3 d until the end of experiment.

3.2. Ecosystem services of G. lemaneiformis in Yantian Bay 3.2.1. Nutrient uptake efficiencies and photosynthetic rates of G. lemaneiformis The O2 production efficiency and C sequestration efficiency of G. lemaneiformis were 21.13 and 9.25 mg/(g DW∙h) in region 1 and 17.29 and 6.68 mg/(g DW∙h) in region 4, respectively. The nutrient uptake efficiency of NH4+-N, NO3−-N, NO2–N, and PO43--P was 56.98 ± 4.81, 23.82 ± 8.79, 7.63 ± 0.64, and 14.54 ± 4.18 μg/(g DW∙h) in region 1 and 38.68 ± 7.12, 22.80 ± 6.18, 9.27 ± 5.35, and 10.21 ± 3.77 μg/(g DW∙h) in region 4, respectively. The removal efficiencies on these nutrients were 53.47%, 3.53%, 11.13%, and 14.57% in region 1 and 26.58%, 3.58%, 16.69%, and 10.84% in region 4, respectively.

2.3. Data analysis All statistical analysis were performed using Origin 8.0 software (OriginLab, USA). The sketch map of location in the present study was created using Surfer 8.0 software (Golden Software, USA). All data are presented as mean ± standard deviation. Tests of homogeneity of variance were conducted, and separate one-way analysis of variance was performed to test for differences in physicochemical parameters and growth properties between different experimental groups. Least significant difference was used to make post hoc comparisons between different experimental groups. Differences were considered to be significant at P < 0.05.

3.2.2. Growth rates and nutrient removal rates of G. lemaneiformis The SGRs of G. lemaneiformis ranged 6.34–13.00%/d, with an average of 9.64%/d during the study period. The SGRs were higher during the first 15 days and there was a significant difference over time (P = 0.000). Fv/Fm was in the range of 0.460–0.513, and there were no significant differences over time (P = 0.924) (Fig. 2). Variations in DO and Chl a were showed in Fig. 3. DO concentration was in the range of 4.507–8.137 mg/L during the period of 27 Oct to 8 Nov, which was significantly higher than that on 24 Oct. The DO concentrations in G. lemaneiformis cultivation areas (region 1 and region 2) and in control area (region 5) were significantly higher than those in the fish cage area (region 4) (P = 0.050–0.080). Chl a concentrations varied greatly during the study period, and decreased to 0.087 mg/L in all investigated regions until 8 Nov. Changes in dissolved inorganic nutrients are summarized in Fig. 4. The NH4+-N concentrations in fish cage area (region 4) were significantly higher than those in other areas (P = 0.000–0.003). Compared with the fish cage area, the nutrient uptake rates of NH4+-N in regions 1 and 2 were in the range of 0.0196–0.0871 mg/L and 0.0134–0.0732 mg/L, respectively, and the maximum removal efficiency were 59.79% and 45.99%, respectively. The concentration of NO3−-N in the region 1 was lower than those in region 3 and region 4 (P = 0.002 and P = 0.014), and the concentration of NO3−-N in the region 2 was lower than that in the region 3 (P = 0.028). Compared with the fish cage area, the nutrient uptake rates of NO3−-N in regions 1 and 2 were in the range of 0.007–0.182 mg/L and 0.003–0.112 mg/L, and the maximum removal efficiency were 30.21% and 13.10%, respectively. The concentration of NO2−-N in the control area (region 5) was lower than those in animal aquaculture areas (region 3 and region

3. Results 3.1. Growth and nutrient uptake of G. lemaneiformis under different nutrient structures in the laboratory 3.1.1. Gracilaria lemaneiformis growth rate The SGRs of all groups decreased with time (Table 2). The variance analysis results showed that N had a significant effect on the SGR of G. lemaneiformis (P = 0.014), but the effect of P on SGR of G. lemaneiformis was not significant (P = 0.935). At 12 h and 36 h, the SGRs in N1 and N2 groups was significantly higher than those in N3 and N4 groups (P = 0.000–0.011). However, the SGRs of G. lemaneiformis were lower than 3.2%/d in all experimental groups at 60 h. 3.1.2. Nutrient uptake rates under different nutrient conditions The N uptake rate of G. lemaneiformis decreased over time (Table 3). There was no significant effect on N and P uptake rate after 60 h between different nutrient conditions (P = 0.078 and P = 0.363, 76

Aquatic Botany 153 (2019) 73–80

Y. Duan et al.

Table 2 Specific growth rates (SGRs) of G. lemaneiformis in the 16 different experimental treatments (%/d). Concentration

Time

P1 (30 μm/L)

P2 (15 μm/L)

P3 (5 μm/L)

P4 (0.5 μm/L)

N1

12 h 36 h 60 h 12 h 36 h 60 h 12 h 36 h 60 h 12 h 36 h 60 h

7.964 3.485 2.359 7.993 4.874 2.779 4.104 3.900 2.868 5.814 1.867 2.415

5.955 3.119 2.874 7.757 3.730 3.052 3.281 2.932 3.165 2.247 1.467 1.381

6.026 3.553 2.515 7.876 4.514 3.073 4.771 2.422 2.988 1.537 1.725 2.168

7.731 3.144 2.807 3.434 3.421 2.276 4.508 3.173 3.113 1.291 1.548 1.902

(500 μm/L) N2 (100 μm/L) N3 (50 μm/L) N4 (5 μm/L)

± ± ± ± ± ± ± ± ± ± ± ±

0.507 0.269 0.208 0.399 0.389 0.323 0.375 0.387 0.293 0.313 0.177 0.155

± ± ± ± ± ± ± ± ± ± ± ±

0.288 0.410 0.261 0.336 0.408 0.301 0.195 0.382 0.281 0.224 0.227 0.188

± ± ± ± ± ± ± ± ± ± ± ±

0.233 0.356 0.257 0.255 0.414 0.180 0.441 0.145 0.212 0.162 0.285 0.087

± ± ± ± ± ± ± ± ± ± ± ±

0.466 0.319 0.387 0.231 0.380 0.078 0.166 0.197 0.069 0.211 0.077 0.101

from 50/3.13 μM to 400/25 μM but decreased significantly when the N/ P ratios exceeded 400/25 μM. In the present study, G. lemaneiformis grew well under different nutrient conditions with N/P levels from 5/ 30 μM (N4P1) to 500/0.5 μM (N1P4), and the growth rate reached up to 5.81%/d and 7.73%/d during the 12 h from beginning, respectively. Even though these results indicated that G. lemaneiformis could obtain relatively high growth rates under different nutrient conditions, the growth rates were higher in high nutrient concentrations than those in low nutrient conditions. The variations of SGRs under high nutrient concentrations were greater than those at low concentrations, which was mainly due to rapid declines in nutrient concentrations over time. Pederson and Borum (1997) studied the ability of six macroalgae species to sustain growth at low N availability by comparing substrate dependent growth kinetics, and their results indicated that fast-growing species tended to require relatively higher external concentrations of inorganic N to saturate their growth, and slow-growing macroalgae may be better able to meet their N requirements at low N availability than fast-growing species. In the present study, G. lemaneiformis showed relatively high nutrient accumulation ability, but extreme high nutrient concentrations also inhibited its absorptive capacity. Abreu et al. (2011b) studied the N uptake responses of G. vermiculophylla under combined and single additions of NO3− and NH4+, and the results showed that high nutrient concentrations had a certain inhibitory effect on nutrient absorption and NH4+ could be absorbed more easily under high nutrient concentrations. Many studies have shown that Gracilaria can effectively remove nutrients through utilization of excessive nutrients (e. g., N and P) in integrated multi-trophic aquaculture systems of fish, scallops, or shrimp co-cultured with macroalgae in eutrophic mariculture areas (Buschmann et al., 1996; Troell et al.,1997; Neori et al., 1998; Jones et al., 2001; Hernández et al., 2006; Yang et al., 2006; Zhou et al., 2006; Huo et al., 2012). The eutrophication index (E values) of Sansha Bay indicates that it is under severe eutrophic conditions (Hu et al., 2013; Wei et al., 2017). In addition, the poor hydrological exchange

4, P = 0.002 and P = 0.001). The maximum removal efficiency of NO2– N was 14.11% in region 1, and 12.88% in region 2, respectively, compared with those in the fish cage area, but there were no significant differences among G. lemaneiformis cultivation, C. gigas and P. crocea cultured areas during the study period (P = 0.115–0.308). The concentration of PO43--P in G. lemaneiformis cultivation areas (region 1 and region 2) and in the control area (region 5) were lower than those in animal cultured areas (region 3 and region 4, P = 0.000–0.004). Compared with the fish cage area, the nutrient uptake rates of PO43--P in region 1 and region 2 was in the range of 0.001–0.041 mg/L and 0.002–0.035 mg/L, and the maximum removal efficiency was 31.49% and 27.07%, respectively.

4. Discussion The rapid development of mariculture, especially intensive aquaculture, has adversely affected coastal and marine ecosystems (Shu et al., 2004). In some mariculture areas, high concentrations of N and P have caused serious environmental problems, which have contributed to increasing eutrophication and ecological imbalance in coastal areas (Feng et al., 2004; Marinho-Soriano et al., 2009). Eutrophication has been linked to a variety of environmental problems, including low dissolved O2, deterioration in water quality and biodiversity of coastal rivers and bays, loss of critical habitats, and growing prevalence of toxic algal blooms (Boyer and Howarth, 2008; Rose et al., 2015). Since macroalgae are important nutrient absorption pumps and removers of excess N and P from the environment (Wei et al., 2017), their growth and nutrient uptake rates under different nutrient concentrations are very important to be understood. Nutrient availability has an important influence on the growth of Gracilaria (Yang et al., 2005). It had been shown that the growth rate of Gracilaria tenuistipitata was the highest when concentrations of total inorganic N reached 4 μmol/L (Wu et al., 1994). Yu and Yang (2008) reported that growth rates of G. lemaneiformis accelerated when the N/P ratios increased

Table 3 Nitrogen uptake rate of G. lemaneiformis in the 16 different experimental treatments (μmol/[g∙h]). Concentration

Time

P1 (30 μm/L)

P2 (15 μm/L)

P3 (5 μm/L)

P4 (0.5 μm/L)

N1

12 h 36 h 60 h 12 h 36 h 60 h 12 h 36 h 60 h 12 h 36 h 60 h

0.428 0.314 0.113 1.352 0.473 0.358 0.913 0.397 0.262 0.067 0.036 0.021

1.385 1.115 1.208 1.603 0.588 0.401 1.099 0.458 0.268 0.056 0.033 0.020

0.344 0.960 0.820 1.323 0.602 0.407 1.165 0.482 0.292 0.089 0.042 0.025

1.255 0.517 0.175 1.358 0.519 0.356 1.146 0.422 0.261 0.072 0.035 0.020

(500 μm/L) N2 (100 μm/L) N3 (50 μm/L) N4 (5 μm/L)

± ± ± ± ± ± ± ± ± ± ± ±

0.071 0.054 0.046 0.033 0.063 0.008 0.051 0.013 0.004 0.004 0.000 0.000

77

± ± ± ± ± ± ± ± ± ± ± ±

0.055 0.006 0.036 0.06 0.031 0.013 0.015 0.013 0.004 0.003 0.000 0.000

± ± ± ± ± ± ± ± ± ± ± ±

0.085 0.033 0.088 0.018 0.010 0.009 0.048 0.014 0.000 0.011 0.000 0.000

± ± ± ± ± ± ± ± ± ± ± ±

0.061 0.010 0.085 0.015 0.054 0.026 0.045 0.025 0.016 0.011 0.000 0.000

Aquatic Botany 153 (2019) 73–80

Y. Duan et al.

Table 4 Phosphorus uptake rates of G. lemaneiformis in the 16 different experimental treatments (μmol/[g∙h]). Concentration

Time

P1 (30 μm/L)

P2 (15 μm/L)

P3 (5 μm/L)

P4 (0.5 μm/L)

N1

12 h 36 h 60 h 12 h 36 h 60 h 12 h 36 h 60 h 12 h 36 h 60 h

0.039 0.033 0.013 0.005 0.023 0.024 0.069 0.034 0.033 0.002 0.002 0.012

0.014 0.007 0.008 0.005 0.007 0.010 0.035 0.024 0.022 0.033 0.026 0.020

0.003 0.008 0.006 0.022 0.016 0.012 0.012 0.010 0.011 0.022 0.022 0.015

0.003 0.002 0.002 0.002 0.000 0.000 0.003 0.002 0.001 0.003 0.002 0.001

(500 μm/L) N2 (100 μm/L) N3 (50 μm/L) N4 (5 μm/L)

± ± ± ± ± ± ± ± ± ± ± ±

.013 0.014 0.005 0.001 0.003 0.000 0.025 0.001 0.002 0.000 0.000 0.005

± ± ± ± ± ± ± ± ± ± ± ±

0.004 0.001 0.003 0.001 0.002 0.001 0.006 0.001 0.003 0.005 0.002 0.001

± ± ± ± ± ± ± ± ± ± ± ±

0.000 0.001 0.000 0.003 0.006 0.004 0.003 0.001 0.003 0.001 0.002 0.002

± ± ± ± ± ± ± ± ± ± ± ±

0.000 0.000 0.000 0.001 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

Table 5 Dissolved inorganic carbon (DIC) uptake rate of G. lemaneiformis in the 16 different experimental treatments (μmol/[g∙h]). Concentration

Time

P1 (30 μm/L)

P2 (15 μm/L)

P3 (5 μm/L)

P4 (0.5 μm/L)

N1

12 h 36 h 60 h 12 h 36 h 60 h 12 h 36 h 60 h 12 h 36 h 60 h

20.95 ± 0.055 9.13 ± 0.084 6.97 ± 0.059 18.28 ± 0.044 9.47 ± 0.005 6.01 ± 0.006 19.71 ± 0.055 7.68 ± 0.004 5.52 ± 0.005 13.12 ± 0.006 6.27 ± 0.009 4.08 ± 0.000

21.55 ± 0.011 7.18 ± 0.008 5.08 ± 0.006 17.46 ± 0.007 6.03 ± 0.003 5.03 ± 0.002 23.33 ± 0.008 9.51 ± 0.001 4.81 ± 0.004 13.62 ± 0.009 6.31 ± 0.005 4.01 ± 0.008

31.25 ± 0.008 7.49 ± 0.010 5.73 ± 0.009 16.68 ± 0.013 8.33 ± 0.008 5.91 ± 0.001 10.49 ± 0.003 8.48 ± 0.005 4.96 ± 0.002 13.58 ± 0.004 6.54 ± 0.000 5.02 ± 0.005

21.19 ± 0.004 8.53 ± 0.006 4.12 ± 0.005 11.08 ± 0.006 6.11 ± 0.004 4.52 ± 0.000 13.04 ± 0.010 7.73 ± 0.012 5.26 ± 0.008 18.49 ± 0.007 7.21 ± 0.008 4.03 ± 0.002

(500 μm/L) N2 (100 μm/L) N3 (50 μm/L) N4 (5 μm/L)

Fig. 2. Specific growth rate (SGR) and maximum photochemical quantum yield (Fv/Fm) of G. lemaneiformis in Yantian Bay.

Fig. 3. Dissolved oxygen (DO) and chlorophyll a (Chl a) variations in Yantian Bay. Note: region 1, region 2, region 3, region 4, and region 5 represent G. lemaneiformis cultivation area, G. lemaneiformis cultivation area, Crassostrea gigas cultured area, Pseudosciaena crocea cage area, and control area, respectively.

conditions could result in a greater risk of red tide occurrence, fish disease, and water column nutrient enrichment (Hu et al., 2013; Wu et al., 2015a, b). Moreover, highly intensive fish cage farming and poor water exchange have negative effects on sediment environments, which may impact benthic community structure (Wu et al., 2015a, b). Furthermore, sediment also serves as one of the major sources of nutrients into the water (Jiang et al., 2010a, b; Sun et al., 2010). In the eutrophic conditions of Sansha Bay, G. lemaneiformis showed good growth performances based on the results of the present study. The average SGR of G. lemaneiformis was 9.65%/d over 28 days, similar to the study conducted in G. lemaneiformis co-cultured with fish

in Jiaozhou Bay (Zhou et al., 2006), G. lemaneiformis co-cultured with fish and scallops in Jiaozhou Bay and Shenao Bay located in the Yellow Sea and East China Sea (Yang et al., 2006), G. chilensis cultivated in fish cage areas in Metri Bay in Chile (Troell et al., 1997), and G. verrucosa in an enclosed sea located in Hangzhou Bay in the East China Sea (Huo et al., 2012). The present study also showed that the removal efficiency of NH4+-N, NO3−-N, NO2–N, and PO43--P was 56.98 ± 4.81, 78

Aquatic Botany 153 (2019) 73–80

Y. Duan et al.

Fig. 4. Variations in dissolved inorganic nutrient concentrations in Yantian Bay. Note: region 1, region 2, region 3, region 4 and region 5 represents G. lemaneiformis cultivation area, G. lemaneiformis cultivation area, Crassostrea gigas cultured area, Pseudosciaena crocea cage area, and control area, respectively.

23.82 ± 8.79, 7.63 ± 0.64, and 14.54 ± 4.18 μg/(g DW∙h) in region 1, and 38.68 ± 7.12, 22.80 ± 6.18, 9.27 ± 5.35, 10.21 ± 3.77 μg/ (g DW∙h) in region 4, respectively, which was significantly lower than those of G. lemaneiformis co-cultured with fish (Sebastodes fuscescens, Ammodytes personatus) in tanks (Yang et al.,2006; Zhou et al., 2006) and co-cultured with scallops (Chlamys farreri) in experimental tanks (Mao et al., 2009). The relative low nutrient removal efficiency in situ conditions was mainly due to the rapid variations in physicochemical environments. Results of the present study showed that G. lemaneiformis is an ideal agent for bioremediation with high growth rates and nutrient removal efficiencies. In addition to supporting the production of seaweed (and their diverse products) and nutrient bioextraction, seaweed cultivation may also provide other ecosystem services (Sondak et al., 2017; Zhang et al., 2017). Bioenergy with C capture and storage represents the combination of bioenergy production and C capture and storage, resulting in the trapping of CO2 in geological reservoirs (Moreira and Pires, 2016). In Asian-Pacific waters, the total production of seaweed has surpassed 2.61 × 106 DW tons, equivalent to over 2.87 × 106 tons CO2 per year (Sondak et al., 2017). In the present study, the C sequestration efficiency of G. lemaneiformis ranged 6.68–9.25 mg/(g DW∙h), which was similar to the results conducted by Yang et al. (2005) in Sanggou Bay, China. These results indicated that G. lemaneiformis possessed a high capacity for C sequestration. The annual output of G. lemaneiformis was evaluated 21,820 tonnes in Yantian Bay, and accordingly, the yearly potential C harvested as G. lemaneiformis products in Yantian Bay would be 792.39 tonnes (Wu et al., 2015b). In addition, G. lemaneiformis would produce 17.29–21.13 mg O2/(g DW∙h) with an average of 19.21 mg O2/(g DW∙h), with was similar to the results of Yang et al. (2005) in Sanggou Bay, China. Furthermore, according to the cultivation scale (1360 tonnes), wet to dry ratio (6.1:1), the cultivation time (September to April), the SGR (9.64%/d) and approximately 12 h of light, the annual output of O2 was around 12,929.23 tonnes in Yantian Bay. Moreover, according to the year's yield of G. lemaneiformis (in this study) and the content of carbon, nitrogen and phosphorus in G. lemaneiformis (Wu et al., 2015b), it was extrapolated that the

1192.03 tonnes of C would be produced, and 128.10 tonnes N and 15.89 tonnes P would be simultaneously sequestered from the seawater, through G. lemaneiformis cultivation in Yantian Bay. These results suggest that G. lemaneiformis cultivated may be an effective way to improve the aquatic environment in eutrophic areas (Wei et al., 2017). In conclusion, G. lemaneiformis, with high growth rates and nutrient removal efficiencies, is a suitable agent for nutrient bioextraction in eutrophic sea areas. Due to its economic and ecological benefits, G. lemaneiformis cultivation is recommended on a global scale. Furthermore, the development and promotion of integrated multitrophic aquaculture systems using G. lemaneiformis co-cultured with aquatic animals requires cooperation between government and farmers in order to achieve sustainable mariculture. Acknowledgements This study was supported by the Public Science and Technology Research Funds Projects of Ocean (201205009-5), Key Projects in the National Science & Technology Pillar Program (2012BAC07B03), the Shanghai Universities First-class Disciplines Project (Discipline name: Marine Science (0707)), the Plateau Peak Disciplines Project of Shanghai Universities (Marine Science 0707). Thanks are also due to the anonymous reviewers for their valuable comments and suggestions. References Abreu, M.H., Pereira, R., Yarish, C., Buschmann, A.H., Sousa-Pinto, I., 2011a. IMTA with Gracilaria vermiculophylla: productivity and nutrient removal performance of the seaweed in a land-based pilot scale system. Aquaculture 312 (1–4), 77–87. Abreu, M.H., Pereira, R., Buschmann, A.H., Sousa-Pinto, I., Yarish, C., 2011b. Nitrogen uptake responses of Gracilaria vermiculophylla (Ohmi) Papenfuss under combined and single addition of nitrate and ammonium. J. Exp. Mar. Biol. Ecol. 407 (2), 190–199. Boyer, E.W., Howarth, R.W., 2008. Nitrogen fluxes from rivers to the coastal oceans. In: Capone, D.G., Bronk, D., Mulholland, M., Carpenter, E.J. (Eds.), Nitrogen in the Marine Environment, second ed. Academic Press, San Diego, pp. 1565–1587. Brawley, S.H., Xiugeng, F., 1988. Ecological studies of Gracilaria asiatica and Gracilaria lemaneiformis in Zhanshan Bay, Qingdao. Chin. J. Oceanol. Limnol. 6 (1), 22–34. Buschmann, A.H., Troell, M., Kautsky, N., Kautsky, L., 1996. Integrated tank cultivation of salmonids and Gracilaria chilensis (Gracilariales, Rhodophyta). Hydrobiologia 326

79

Aquatic Botany 153 (2019) 73–80

Y. Duan et al.

New York, pp. 1–33. Shu, T.F., Wen, Y.M., Jia, H.L., Xu, X.R., Wang, W.Q., Yang, L., 2004. Influence of cage culture in Yaling Bay on water environment. Environ. Sci. 25 (5), 97–101 in Chinese with English abstract. Skriptsova, A.V., Miroshnikova, N.V., 2011. Laboratory experiment to determine the potential of two macroalgae from the Russian Far-East as biofilters for integrated multi-trophic aquaculture (IMTA). Bioresour. Technol. 102 (3), 3149–3154. Sondak, C.F.A., Ang, P.O., Beardall, J., Bellgrove, A., Boo, S.M., Gerung, G.S., Hepburn, C.D., Hong, D.D., Hu, Z., Kawai, H., Largo, D., Lee, J.A., Lim, P., Mayakun, J., Nelson, W.A., Oak, J.H., Phang, S., Sahoo, D., Peerapornpis, Y., Yang, Y., Chung, I.K., 2017. Carbon dioxide mitigation potential of seaweed aquaculture beds (SABs). J. Appl. Phycol. 29 (5), 2363–2373. Sun, S., Liu, S.M., Ring, J.L., Zhang, J.H., Jiang, Z.J., 2010. Distribution features of nutrients and flux across the sediment-water interface in the Sanggou Bay. Acta Oceanolog. Sin. 32 (6), 109–117 in Chinese with English abstract. Troell, M., Halling, C., Nilsson, A., Buschmann, A.H., Kautsky, N., Kautsky, L., 1997. Integrated marine cultivation of Gracilaria chilensis (Gracilariales, Rhodophyta) and salmon cages for reduced environmental impact and increased economic output. Aquaculture 156 (1–2), 45–61. Troell, M., Jonell, M., Henriksson, P.J.G., 2017. Ocean space for seafood. Nat. Ecol. Evol. 1 (9), 1224. Troell, M., Rönnbäck, P., Halling, C., Kautsky, N., Buschmann, A., 1999. Ecological engineering in aquaculture: use of seaweeds for removing nutrients from intensive mariculture. J. Appl. Phycol. 11, 89–97. Tseng, C.K., 2001. Algal biotechnology industries and research activities in China. J. Appl. Phycol. 13 (4), 375–380. Wang, Y., Yu, Z., Song, X., Tang, X., Zhang, S., 2007. Effects of macroalgae Ulva pertusa (Chlorophyta) and Gracilaria lemaneiformis (Rhodophyta) on growth of four species of bloom-forming dinoflagellates. Aquat. Bot. 86 (2), 139–147. Wei, Z., You, J., Wu, H., Yang, F., Long, L., Liu, Q., Huo, Y., He, P., 2017. Bioremediation using Gracilaria lemaneiformis to manage the nitrogen and phosphorous balance in an integrated multi-trophic aquaculture system in Yantian Bay, China. Mar. Pollut. Bull. 121, 313–319. Wu, C.Y., Li, R.Z., Lin, G.H., Wen, Z.C., Zhang, J.P., Dong, L.F., Huang, X.H., 1994. Study on the optimum environmental parameters for the growth of Gracilaria tenuistipitatavar. liui in pond culture. Oceanol. Limnol. Sin. 25, 60–66 in Chinese with English abstract. Wu, H., Huo, Y., Han, F., Liu, Y., He, P., 2015a. Bioremediation using Gracilaria chouae cocultured with Sparus macrocephalusto manage the nitrogen and phosphorous balance in an IMTA system in Xiangshan Bay, China. Mar. Pollut. Bull. 91 (1), 272–279. Wu, H., Huo, Y., Hu, M., Wei, Z., He, P., 2015b. Eutrophication assessment and bioremediation strategy using seaweeds co-cultured with aquatic animals in an enclosed bay in China. Mar. Pollut. Bull. 95 (1), 342–349. Wu, R.S.S., 1995. The environmental impact of marine fish culture: towards a sustainable future. Mar. Pollut. Bull. 31 (4–12), 159–166. Fei, X., Ying, B., Shan, L., 1999. Seaweed cultivation: traditional way and its reformation. Chin. J. Oceanol. Limnol. 17 (3), 193–199. Xu, Z., Gao, K., 2012. NH4+ enrichment and UV radiation interact to affect the photosynthesis and nitrogen uptake of Gracilaria lemaneiformis (Rhodophyta). Mar. Pollut. Bull. 64 (1), 99–105. Yang, H.S., Zhou, Y., Mao, Y.Z., Li, X.X., Liu, Y., Zhang, F.S., 2005. Growth characters and photosynthetic capacity of Gracilaria lemaneiformis as a biofilter in a shellfish farming area in Sanggou Bay, China. J. Appl. Phycol. 17 (3), 199–206. Yang, Y., Fei, X., 2003. Prospects for bioremediation of cultivation of large-sized seaweed in eutrophic mariculture areas. J. Ocean Univ. Qingdao 33 (1), 53–57. Yang, Y.F., Fei, X.G., Song, J.M., Hu, H.Y., Wang, G.C., Chung, I.K., 2006. Growth of Gracilaria lemaneiformis under different cultivation conditions and its effects on nutrient removal in Chinese coastal waters. Aquaculture 254 (1–4), 248–255. Yao, H., Yu-ze, M., Yi, Z., Zeng-jie, J., Dong-zhe, W., Ting-ru, Y., Jian-guang, F., 2013. Field study on photosynthetic carbon acquisition of Gracilaria lemaneifomis after adding nitrogen and phosphorus. Progress Fish. Sci. 34 (1), 22–30 in Chinese with English abstract. Ye, N., Wang, H., Wang, G., 2006. Formation and early development of tetraspores of Gracilaria lemaneiformis (Gracilaria, Gracilariaceae) under laboratory conditions. Aquaculture 254 (1–4), 219–226. Yu, J., Yang, Y.F., 2008. Physiological and biochemical response of seaweed Gracilaria lemaneiformis to concentration changes of N and P. J. Exp. Mar. Biol. Ecol. 367 (2), 142–148. Zhang, Y., Zhang, J., Liang, Y., Li, H., Li, G., Chen, X., Zhao, P., Jiang, Z., Zou, D., Liu, X., Liu, J., 2017. Carbon sequestration processes and mechanisms in coastal mariculture environments in China. Sci. China Earth Sci. 60 (12), 2097–2107. Zhou, Y., Yang, H., Hu, H., Liu, Y., Mao, Y., Zhou, H., Xu, X., Zhang, F., 2006. Bioremediation potential of the macroalga Gracilaria lemaneiformis (Rhodophyta) integrated into fed fish culture in coastal waters of north China. Aquaculture 252 (2–4), 264–276. Zou, D., Xia, J., Yang, Y., 2004. Photosynthetic use of exogenous inorganic carbon in the agarophyte Gracilaria lemaneiformis (Rhodophyta). Aquaculture 237 (1–4), 421–431.

(1), 75–82. Chen, C.L., Qiu, G.H., 2014. The long and bumpy journey: taiwan’s aquaculture development and management. Mar. Policy 48, 152–161. Chopin, T., Buschmann, A.H., Halling, C., Troell, M., Kautsky, N., Neori, A., Kraemer, G., Zertuche-Gonzalez, J., Yarish, C., Neefus, C., 2001. Integrating seaweeds into marine aquaculture systems: a key toward sustainability. J. Phycol. 37 (6), 975–986. Chung, I.K., Kang, Y.H., Yarish, C., Kraemer, G.P., Lee, J.A., 2002. Application of seaweed cultivation to the bioremediation of nutrient-rich effluent. Algae 17 (3), 187–194. Fei, X., 2004. Solving the coastal eutrophication problem by large scale seaweed cultivation. Hydrobiologia 512, 145–151. Feng, Y.Y., Hou, L.C., Ping, N.X., Ling, T.D., Kyo, C.I., 2004. Development of mariculture and its impacts in Chinese coastal waters. Rev. Fish Biol. Fish. 14 (1), 1–10. Ferreira, J.G., Saurel, C., e Silva, J.D.L., Nunes, J.P., Vazquez, F., 2014. Modelling of interactions between inshore and offshore aquaculture. Aquaculture 426, 154–164. Hernández, I., Pérez-Pastor, A., Vergara, J.J., Martínez-Aragón, J.F., Fernández-Engo, M.Á., Pérez-Lloréns, J.L., 2006. Studies on the biofiltration capacity of Gracilariopsi slongissima: from microscale to macroscale. Aquaculture 252 (1), 43–53. Hu, M., Wei, Z.L., Han, H.B., Cui, J.J., Huo, Y.Z., 2013. The survey and assessment of water environmental quality in the mariculture area in the enclosed Sansha Bay. J. Shanghai Ocean Univ. 23 (4), 582–587 in Chinese with English abstract. Huo, Y., Zhang, J., Xu, S., Tian, Q., Zhang, Y., He, P., 2011. Effects of seaweed Gracilaria verrucosaon the growth of microalgae: A case study in the laboratory and in an enclosed sea of Hangzhou Bay, China. Harmful Algae 10 (4), 411–418. Huo, Y., Wu, H., Chai, Z., Xu, S., Han, F., Dong, L., He, P., 2012. Bioremediation efficiency of Gracilaria verrucosa for an integrated multi-trophic aquaculture system with Pseudosciaena crocea in Xiangshan Harbor, China. Aquaculture 326, 99–105. Jiang, Z.J., Fang, J.G., Mao, Y.Z., Wang, W., 2010a. Eutrophication assessment and bioremediation strategy in a marine fish cage culture area in Nansha Bay, China. J. Appl. Phycol. 22 (4), 421–426. Jiang, Z.J., Fang, J.G., Mao, Y.Z., Wang, W., Shi, H.X., Jiao, H.F., 2010b. Diffusion fluxes of dissolved inorganic nitrogen and phosphorus across sediment-water interface in Nansha Aquaculture Area, China. J. Agro-Environ. Sci. 29 (12), 2413–2419 in Chinese with English abstract. Jones, A.B., Dennison, W.C., Preston, N.P., 2001. Integrated treatment of shrimp effluent by sedimentation, oyster filtration and macroalgal absorption: a laboratory scale study. Aquaculture 193 (1–2), 55–178. Klenell, M., Snoeijs, P., Pedersén, M., 2004. Active carbon uptake in Laminaria digitata and L. saccharina(Phaeophyta) is driven by a proton pump in the plasma membrane. Hydrobiologia 514, 41–53. Lin, A., Wang, C., Qiao, H., Pan, G., Wang, G., Song, L., Wang, Z., Sun, S., Zhou, B., 2009. Study on Photosynthesis of Qingdao sea floating and settlement of Enteromorpha. Chin. Sci. Bull. (3), 294–298. Liu, O.R., Molina, R., Wilson, M., Halpern, B.S., 2018. Global opportunities for mariculture development to promote human nutrition[R]. Peer J. Preprints. Lu, H., Xie, H., Gong, Y., Wang, Q., Yang, Y., 2011. Secondary metabolites from the seaweed Gracilaria lemaneiformis and their allelopathic effects on Skeletonema costatum. Biochem. Syst. Ecol. 39 (4–6), 397–400. Mao, Y.Z., Yang, H.S., Zhou, Y., Ye, N.H., Fang, J.G., 2009. Potential of the seaweed Gracilaria lemaneiformis for integrated multi-trophic aquaculture with scallop Chlamys farreri in North China. J. Appl. Phycol. 21 (6), 649. Marinho-Soriano, E., Panucci, R.A., Carneiro, M.A.A., Pereira, D.C., 2009. Evaluation of Gracilaria caudata J. Agardh for bioremediation of nutrients from shrimp farming wastewater. Bioresour. Technol. 100 (24), 6192–6198. Moreira, D., Pires, J.C.M., 2016. Atmospheric CO2 capture by algae: negative carbon dioxide emission path. Bioresour. Technol. 215, 371–379. Moulin, P., Andría, J.R., Axelsson, L., Mercado, J.M., 2011. Different mechanisms of inorganic carbon acquisition in red macroalgae (Rhodophyta) revealed by the use of TRIS buffer. Aquat. Bot. 95 (1), 31–38. Neori, A., Chopin, T., Troell, M., Buschmann, A.H., Kraemer, G.P., Halling, C., Shpigel, M., Yarish, C., 2004. Integrated aquaculture: rationale, evolution and state of the art emphasizing seaweed biofiltration in modern mariculture. Aquaculture 231 (1–4), 316–391. Neori, A., Ragg, N.L.C., Shpigel, M., 1998. The integrated culture of seaweed, abalone, fish and clams in modular intensive land-based system: II. Performance and nitrogen partitioning within an abalone (Haliotis tuberculata) and macroalgae culture system. Aquac. Eng. 17 (4), 215–239. Ottinger, M., Clauss, K., Kuenzer, C., 2016. Aquaculture: relevance, distribution, impacts and spatial assessments–a review. Ocean Coast. Manag. 119, 244–266. Packer, M., 2009. Algal capture of carbon dioxide; biomass generation as a tool for greenhouse gas mitigation with reference to New Zealand energy strategy and policy. Energy Policy 37 (9), 3428–3437. Pederson, M.F., Borum, J., 1997. Nutrient control of estuarine macroalgae: growth strategy and the balance between nitrogen requirements and uptake. Mar. Ecol. Prog. Ser. 161, 155–163. Rose, J.M., Bricker, S.B., Deonarine, S., Ferreira, J.G., Getchis, T., Grant, J., Kim, J.K., Krumholz, J.S., Kraemer, G.P., Stephenson, K., 2015. Nutrient bioextraction. In: Meyers, R.A. (Ed.), Encyclopedia of Sustainability Science and Technology. Springer,

80