Depth zonation of epibenthos on sublittoral hard substrates off Deer Island, Bay of Fundy, Canada

Estuarine, Coastal and Shelf Science (1984) 18, 57 l-592

Depth Zonation Hard Substrates Fundy, Canada

A. Logana,

of Epibenthos on Sublittoral off Deer Island, Bay of

F. H. Pageb and M. L. H. ThomasC

aDepartment of Geology, University of New Brunswick, Saint John, New Brunswick; bDepartment of Oceanography, Dalhousie University, Halifax, Nova Scotia and ‘Department of Biology, University of New Brunswick, Saint John, New Brunswick, Canada Received 21 February 1983 and in revised form 28 July 1983

Keywords:

sublittoral

zones; benthos; depth zones; Bay of Fundy, Canada

Three locations were selected for detailed study of the epibenthos of sublittoral hard substrates in the Deer Island region of the Bay of Fundy. A total of 10 transects, using photographic and quadrat methods, yielded data on percentage coverage, density and diversity of biota in relation to depth. A cluster analysis, using the Jaccard Coefficient of Association, produced five major clusters, representing three depth zones. The shallow and mid-depth zones lie within the infralittoral, the deep zone within the circalittoral. The shallow zone extends from mean low water (MLW) to a mean depth of 5 m below MLW and consists of two clusters representing minor biological differences. It is characterized by crustose coralline algae and Petrocelis middendorjii which together cover over 70% of the primary substrate. Other macro-algae are rare, as are bryozoans, while sponges are absent. The sea urchin Strongylocentrotus droebachiensis, the limpet Acmaea testudinalis and chitons belonging to Tonicella are very common and may exert a significant influence on the community structure in terms of grazing pressure. The mid-depth zone has a mean depth of 10m and consists of two clusters, one representing well-illuminated upward-facing surfaces, the other representing shaded steeply-inclined cliff faces. The zone is characterized by higher species richness (relative to the shallow zone); greater coverage of sponges, bryozoans and hydroids; lower densities of sea urchins and limpets; and less area1 coverage by encrusting algae. The cliff-face cluster is characterized by enrichment of bryozoans, anemones, sponges and brachiopods. The deep zone has a mean depth of 18 m, and is animal-dominated, supporting the greatest species richness, with sponges, hydroids, anemones, brachiopods and tunicates common, but algal coverage much reduced. Organisms colonizing the upward-facing surfaces in the shallow and mid-depth zones are here regarded as belonging to the encrusting algae-urchin community, while biota of the shaded cliff faces of the mid-depth zone, together with the biota of the deep zone, are regarded as belonging to the Terebratulina septentrionalis community of previous authors.

Introduction While there is a large volume of literature devoted to the study of epibenthic communities on sublittoral hard substrates (mainly coral reefs) from low latitudes, such communities 571 027.h7714/84/050571+22

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A. Logan,F. H. Page& M. L. H. Thomas

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from higher latitudes have received relatively little attention, although important studies have been conducted in the Mediterranean Sea (see literature review in Logan, 1979) and, to a lesser extent, in the British Isles (e.g. Hiscock & Hoare, 1975; Knight-Jones & Nelson-Smith, 1977; Hoare & Peattie, 1979; Hiscock & Mitchell, 1980), Scandinavia (e.g. Lundllv, 1971; Gulliksen, 1974, 1977, 1978; Jansson& Kautsky, 1977); New Zealand (Grange et al., 1981) and the Antarctic (Dayton et al., 1970, 1974). Studies on natural sublittoral animal-dominated hard substrate communities of the east coast of North America are relatively few (e.g. Noble et al., 1976; Osman, 1977; Hulbert et al., 1980), for most have been concerned mainly with the distribution and associationsof macro-algae (for references, see Sears& Wilce, 1975). The reverse trend is shown in a survey of the literature of rocky shore intertidal communities; that is, shores of higher latitudes have received much more extensive study than those of low latitudes. From the voluminous literature on this subject, it is only necessary here to acknowledge the contributions of such investigators as Connell, Dayton, Lewis, Lubchenko, Menge, Paine, Sousa, Southward, the Stephensonsand Vadas (see literature review in Thomas et al., 1983). Most of these workers have been concerned primarily with the nature of rocky shore intertidal zonation, but somehave, by manipulative experiments, been able to evaluate the relative importance of physical and biological factors, either acting singly or in combination. However, difficulties associatedwith carrying out experiments in the sublittoral have led to little more than basic descriptions of epibenthic zonation from relatively few localities. It is clear from studies that have been initiated, however, that sublittoral communities are more complex than those of the intertidal (Harris et al., 1979; Hulbert et al., 1980). Extensive occurrences of rocky substratesin shallow, relatively clear coastal waters in the western part of the Bay of Fundy support rich epibenthic communities. Resource surveys (Neish, 1973a, b; MacKay, 1978a, 6, c, 1979) and research studies (Logan & Noble, 1971; Noble et al., 1976) have establishedthe broad patterns of geographic distribution of the main biotic elements, as well as their contribution to the sediments,in the Quoddy Region of New Brunswick. In a recent review of sublittoral epibenthic communities in the western part of the Bay of Fundy (Logan et al., 1983), two major communities were recognized down to about 30 m below MLW, where hard substrates are normally succeededby sediments.Encrusting algae, mainly corallines, colonize all well-illuminated upper surfaces and occur in associationwith a diverse fauna, both sessileand mobile, the most prominent member of which is the green seaurchin Strongylocentrotusdroebachiensis. This community was described qualitatively by Noble et al. (1976) but no detailed quantitative studies have been performed. The second community, the Terebratulina septem-ionuliscommunity, inhabits the undersides of boulders in shallow water, but becomesmore emergent with increasing depth. This community has been quantitatively described (Noble et al., 1976), along four transects from MLW to 24 m off eastern Deer Island. The present study quantitatively describesthe encrusting algae-urchin community and establishesthe existence of a depth-related zonation pattern for sublittoral epibenthos in the Quoddy region of the Bay of Fundy. The study has broader implications, since the area in question is dominated by sea urchins, with few associatedmacro-algae including kelps. It is therefore a stage in the postulated conversion of highly-productive north temperate kelp bedsto poorly-productive urchin-dominated barren grounds (Mann, 1972, 1977; Chapman, 1981). A third rationale for this study is the possibility of the construction of an oil refinery at Eastport, Maine and future oil-drilling in the Bay of Fundy, as an extension of Scotian

Depth zonation of sublittoral epibenthos

573

3

Figure 1. Map of Deer (T) at each site.

Island and vicinity,

showing

sample sites and number

of transects

Shelf exploration. The present study provides much-needed base-line data on benthos in the event of pollution in the region. Study area Deer Island forms part of the Quoddy region of southern New Brunswick, bounded by a line extending from Point Lepreau to the north-east tip of Grand Manan Island and proceeding to West Quoddy Head in Maine (Thomas, 1983~). The physical oceanography and meteorology of this region are described by Trites and Garrett (1983) and Thomas (1983b). Deer Island and surrounding small islands form an archipelago separating PassamaquoddyBay from the Bay of Fundy (Figure 1). The geology of the islands is dominated by volcanic and metasedimentaryrocks of probable Silurian age (Alcock, 1946). Such resistant rocks weather to produce a relatively steep zone of submergedrock debris ranging from boulder to pebble size, alternating with ledges of submergedrock outcrop. Some of the outer islands, such as Casco, Spruce and White, have outcrops of Devonian Perry Formation conglomerateswhich result in lesssteeply-inclined and lessfissured rock surfaces and greater production of boulders and sediment. The dominant hydrographic feature of the area is the large mean tidal range of 5 ‘3 m of water flowing at each tidal cycle through relatively constricted channelsbetween the islands, such as Letite Passageand Head Harbour-Western Passage.This results in relatively high tidal current velocities reaching maxima of up to 2 m s-1 (Forrester, 1960;

574

A. Logan, F. H. Page& M. L. H. Thomas

Gaskin et al., 1979; Trites & Garrett, 1983). Velocities are much less around islands not in these main channels, but still sufficient to prevent significant sediment accumulation in shallow zones. Salinities are relatively constant with depth and time throughout the area, ranging between 30 and 32%0(Trites & Garrett, 1983), while water temperatures vary seasonally, ranging from 0.5’ to 14 “C (Bailey et al., 1954; Trites & Garrett, 1983). Thermoclines and pycnoclines are not normally present. Light intensity and penetration are extremely variable diurnally, seasonallyand annually, depending on the tidal cycle, river runoff, fog and algal blooms. Generally, however, penetration and underwater visibility are less than that for average coastal waters of the Gulf of Maine, the greatest water clarity occurring in the winter and the lowest in summer (MacKay, 1978~). Normal underwater horizontal visibility is in the order of 8 m (personal observation). Wave action is generally low throughout the Deer Island archipelagodue to its protective land masses,with the exception of southerly exposuresof Spruce, White and Whitehorse Islands, which are subject to swell from the Gulf of Maine. Methods Site selection Sampling sites were carefully selected with the following considerationsin mind: all sites should show little or no physical disturbance, such asoverturning of boulders, which could affect the community structure (Osman, 1977); rock outcrop and large boulders should predominate over small boulders; and locations should have steeply-sloping bottom profiles, to reduce sampling time and variation in community structure due to heterogeneity of slope. With these criteria in mind, three sites were finally selected: Simpson Island (western side), Spruce Island (eastern side) and CascoIsland (southern side). The location of these sites is shown in Figure 1 along with the number of transects at each site. The SimpsonIsland site is relatively sheltered and showsalmost complete bedrock down to 13 m, forming ledges and cliffs in which cracks and crevices are common in the highlycleaved volcanic rocks. Four transects, all within 100m of each other, were selected on the basisof the criteria listed above; their proties are shown in Figure 2. The slope of the substrate between each interval of transect line was calculated for all transects. Slope distributions in intervals of 15 ’ are shown in Figure 2. SimpsonIsland profiles are characterized by a high frequency of vertical (75-90°C) cliff faces and very few horizontal expanses.In contrast to the previous site, both Spruce Island and CascoIsland lie adjacent to the deep Head Harbour Passageand are composedof shallow-dipping Perry Formation conglomerate, which has fewer cracks and crevices. At Spruce Island, the four bottom profiles surveyed (again, all within 100m of one another) drop precipitously to a depth between 7 and 13 m before levelling off to a near-horizontal ledge, which grades into sandy sediment (Figure 2). In all slope categories Spruce Island profiles have frequency distributions intermediate to those at Simpsonand CascoIslands (Figure 2). Two adjacent transects were run perpendicular to the coast on the south side of Casco Island. These are the deepest transects surveyed and show a predominanceof near-horizontal surfaces. Samplingtechnique In total, 10 underwater transects were run at right-angles to the shore at three siteschosen, during July and August of 1980. SCUBA was employed to obtain bottom profiles of each

575

Depth zonation of sublittoral epibenthos

-4

(01 0

Srnpson

---

Percentage

Island

of surface

irradnnce

i lag 1

t

Wave energy ond current velocity low, E.I. = 5,27 16.

I 02

’ 01

-4 - (b)

Spruce

I 04

I 03 Island

I OS

24 -4

Cc i Casco

Island ----

0--

----MLLt

,

4veimty

8-

hgb,

EI : 5-32 12-

24

0 q

Bedrock Sand

Figure 2. Bottom profiles of 10 transects from the three study sites chosen (a)-(cj; mean frequency of slope inclinations at 15” intervals throughout total depth range of transects (AI-C’); and logarithmic plot of percentage surface irradiance, based on mean values for Simpson Island transects, 14,18 and 19 August, 1980 (AZ). E.I. = Exposure Index (Thomas, in press). Black dots mark photographic sites and approximate positions of quadrat sites.

transect and to samplethe biota along eachtransect, using a stratified random sampledesign (Scheaffer er al., 1979). Within each 4.6m segment of transect line, seven close-up photographs were taken as contiguously as possible, each photograph covering an area of 311 cmz, to give a total sample area per segmentof 2177cm2. The photographic methodology for estimating cover is described by Logan et al. (1983) and is identical to that used by Gulliksen (1974, 1978). While the sampling area falls short of that recommendedby Weinberg (1978) it doesexceed that usedsuccessfully by Boudouresque (1974) and Chardy

576

A. Logan, F. H. Page & M. L. H. Thomas

(1970) in the Mediterranean sublittoral. Species-area curves were drawn for every depth interval for all transects to test the validity of using this sampling area. In almost all cases, curves level out, suggesting an adequate sampling area. The few exceptions were from the mid-depth range, where overlapping communities may produce a local ecotone effect resulting in higher diversity community structure. It was impossible to maintain total contiguity for the photographs, due to the vagaries of surface relief and change of surface orientation. The photo-transects, supplemented by collections of representative specimens, were the main sampling units used; however, they could not adequately sample the large and sometimes patchily distributed species, whose density was counted using a stratified random sample design where two 1 mz quadrats were randomly placed within each 4 ‘6 m segment of each transect. Treatment of data Photographic transparencies were analysed under a stereomicroscope, using transmitted light. Percentage coverage of organic and inorganic categories was estimated using a transparent overlay of 100 random points (Bohnsack, 1979); also available from each photograph was information on presence/absence and density for easily recognizable species. However, resolution was sometimes not high enough to distinguish species of sponges, hydroids and crustose coralline algae, and in these cases higher taxonomic categories were used. The cluster analysis, using presence/absence data, was based on Jaccard’s Coefficient of Association [Sj = p/ip + n)] where ‘p ’ represents positive matches and ‘ n ’ negative matches. A matrix of similarity of values for each pair of samples was obtained, using the weighted-pair method of clustering (Sokal & Sneath, 1963; Bonham-Carter, 1967). Light, exposure and current measurements Light was measured using an integrating quantum scalar irradiance meter (Biospherical Instruments Inc. Model Q Sl-140) with a spherical collector, operating over the spectral range of 400-700 nm. Readings were taken adjacent to the bottom at 3 m depth intervals, with a 2-5 min recording time at each interval. All measurements were made at Simpson Island on 14, 18 and 19 August, 1980, in the afternoon during uniform light conditions and the results pooled for all four transects at this locality to give a sample summer irradiance curve for this site (Figure 2), which we believe to be reasonably typical of the Deer Island region as a whole. Standard current meters anchored to the bottom lack the sensitivity to record microcurrents affecting benthos and therefore the method of Muus (1968) was used, where the disintegration rate (expressed as percentage weight loss h-i) of plaster-of-Paris balls of 2.5 cm diameter, bolted to the bottom at 3 m depth intervals along each transect, is an index of the relative strength of all water movements around it. Wave action water movement diminishes with depth, but it is active to at least our deepest site. Exposure indices based on the direction of the shore relative to wind energy, fetch and modifying effect of shallow water (Thomas, in press) were calculated. These relative water movement strengths, as well as the exposure indices, are shown qualitatively on the profiles in Figure 2. Results

and discussion

Abundance-depth relationships of major organic and inorganic categories The following abundance-depth relationships are based on either analyses of sets of seven photographs (comprising a total sample area of 2177 cm2 per segment of transect line) to

Crustose coralline algae Petrocelis middendorfii Acmaea testudinalis Tonicella spp. Hydroids Bryozoans Sponges Colonial tunicates Gonactinia sp. Gnshella rufbranchialis Terebratulina septentrionalis Myxicola infundibulum Bare rock Sediments

Category

TABLE

0

2 4.6 14.6

0

1 37.6 13.3

level,

0

0

P = Significance

20.2 15 0 0 0 0 10 46

15.7 0 0 0 0 0 0 0

C D D C C C D D

52,7

4.1

27,4

0.8

7.8

11 1.8 17.0

49

0

NS

P

S

(D)

17.5 10.6

0

1 0 0 0 10 1

22.4

38.3

1.4

3.2

NS

P

42,9

0.8

NS

5NSl 0.3 NS 50.6 NS

96

ONSO

(P
27.4 5.2

0

8.2 NS 13.6 7 NS 2 5 NS 1 0 NSO 1.6NS 0 5.4 NS 0 23 NSO 224 NS 0

S = significant

1 3.7 13.5

5

0

47.9 5 7 0 0 2.2 14 44

12,9

6.9

26.9

8.4

0.3 25.2

81

HS = highly

25 1.0 29.5

4

00

15 0.3 35.7

2

NS

P

46.6

1.8

0 9.5 12.8

0

(P~O.005)

S NS NS

NS

8 0.8 26.3

12

00

37.3 17 15 0.3 0.7 4.5 25 194

9.6

5.8

Transect

Island transects

NS 20.0 NS 3 S 13 NS 0 NS 0 NS 0 NS 0 NS 0 ONSO

1.3 2 20 0 0 3.0 0 7

54.7

significant

11 0 38.2

18

0

9.1 2 23 0 1.4 0.4 0 4

34.9

11.0

12.8

for Simpson

3 (m depth)

interval

49.7 11.1 19 0 12 16 0 1.2 0 2.5 1.4 18.2 00 57 53

8,2

4.3

Transect

per 2177 crnr for each depth

2 (m depth)

21.3

Transect

(P>O.O5),

3NS0 2.0 NS 25.8 NS

42

ONSO

28.8 NS 4NS2 13 NS 0.2NS 5.7 NS 0 NS 1 NS 0 NS

25.2

10.8

NS = not significant

12 0.3 16.4

29

0

28.4 6 20 0 4.8 9.3 7 0

32.8

10.2

1 (mdepth)

35.9 5 6 2.3 0 0 9 30

21,3

Transect

1. Mean percentage cover (C) or total density categories, based on photographic analysis

C

inorganic

0.3 34.4

3

95

1.4 1 16 1.1 5.2 5.2 27 130

40.6

9.4

1 0.3 23.8

18

0

6.4 5 17 1.3 2.6 0.3 0 1

59.6

11.8

4 (m depth)

NS NS NS

NS

NS

NS NS NS NS NS NS NS NS

NS

P

and

S NS NS

NS

NS

NS NS S NS NS NS NS NS

NS

3 Ea, 6

l-4 for major organic

Crustose coralline algae Petrocelis middendorji Acmea testudinalts Tonicella spp. Hydroids Bryozoans Sponges Colonial tunicates Gonactinia sp. Gnyphella @branch&s Terebratulina septentrionalts Myxicola infundibulum Bare rock Sediments

Category

0

0 19.0 0

D C C 0 6.6 0.7

0

7.3 4 1 0 0 0 0 2 0

8.3 10 2 0 0 0 0 0 0

D

81.4

4.0

68.0

1 .o

0 2.7 0.4

0

56.8 2 3 0 0 0 0 0 0

33.3

8.5

Transect

1 0.4 5.6

0

69.3 21 19 4.6 0 0 1 3 1

18.3

11.0

5 (m depth)

0 0.1 9.7

0

17.3 7 13 0 0.1 0 0 0 7

63.2

13 ,o

0 0 23.7

0

11.4 6 36 0.7 2.4 0 1 0 1

60.3

14.5

NS S NS

NS

NS NS NS NS NS NS NS NS NS

NS

P

0 4.7 5-7

0

45 1 23 7 0 0 0 2 0 0

35.1

2.4

TABLE 2. Mean percentage coverage (C) or total density (D) per 2177 cm* for each depth and inorganic categories, based on photographic analysis (letters as in Table 1)

0 0 9.1

1

46.5 22 6 5.7 0 4.2 7 5 6

20.3

6.3

interval

0 0.8 0.4

0

10.5 30 5 0 0 0 0 0 0

86.0

8.2

Transect

for Spruce

0 0 0.7

0

22.3 6 3 0 0 0 0 0 0

74,3

9.9

6 (m depth)

Island transects

0 0 1.1

0

9.0 17 8 0 0 0 0 0 2

84.3

10.6

0 0 4.7

0

39.1 16 7 0.7 0 0 2 0 1

49,6

11.9

5-8 for major

NS NS NS

NS

NS NS NS NS NS NS NS NS NS

NS

P

organic

31 ,o 7 3 0.3 0 0 3 0

0

64.4 7 11 9.1 0 1.3 0 5

1

0

0 0.3 2.6

1.7 17 1 0 0 0 0 0

0

0

0 13.6 0

0 6 1 0 0 0 0 0

0

0

0 11.8 0

0 0 0.5

0

53.0

17.8

79.0

68.8

10.6

8.4

4.3

7 (m depth)

0.5

Transect

27.3 14 8 0.8 0 0 0 0

67.4

0 0 18.3

0

1

9.8 5 10 3.6 0.1 0 1 0

34.1

12.6

NS s NS

NS

NS

NS NS NS NS NS NS NS NS

NS

P

0 0 0

0

0

53.7 13 1 0.1 0 0 0 0

35.1

2.2

0 7.3 0.1

0

0

3.6 5 1 0.6 0 0 0 0

80.8

5.5

0 1.4 2.7

0

1

38.8 2 23 6.4 0.1 10.1 0 7

19.1

9.5

4 0.4 9.0

0

8

0.7 0 20 18.8 0.1 6.5 0 18

28.8

11.0

14 1 12.6

1

1

1.4 2 8 19.6 0.7 14.6 2 52

28.8

12.4

Transect

0 1 9.5

0

2

4.7 0 22 9.2 0 0 0 1

54.8

12.9

8 (m depth)

0 2 17.5

0

1

1.8 0 17 6.3 0 11.4 0 0

43.0

0 5.6 20.4

0

1

4.8 2 19 6.8 0.1 10.6 0 0

44.6

15.7

0 0.8 33.8

7

8

0.1 0 8 27.9 0.3 17.9 4 4

14.6

17.4

0 4.7 22.3

19

1

0 0 0 14.8 1.6 36.5 8 1

0

NS NS HS

S

NS

S S NS NS NS NS NS NS

NS

S HS HS

NS

NS

NS HS S NS NS NS NS NS

NS

Crustose coralline algae Perrocelis middendorji Acmuea testudinalis Tonicella spp. Hydroids Bryozoans Sponges Colonial tunicates Gonactina sp. Coryphella wjbmnchialis Terebratulina septentrionalis Myxicola infundibulum Bare rock Sediments

Category

0

5 0.6 4.3

0

D

DO C 25.1 c 4.4

1

0

33.1 1 25 0.3 O,l 0 7 0

C 42.1 D 0 D 5 c 0 c 0 co D 0 D 0

D

49.3

3.5

10.4

c

0.1

0 l-6 0

16

10

28.7 4 17 0.3 6.8 13-l 3 18

17.0

7.6

0 2.8 9.0

0

4

8.6 1 25 3.1 0 7.6 12 0

51.0

12.1

17.7

14.7

6 0 6.8

5

25

23 18 0 O-l 9.6

0 0 8.4 0

0 0 0 5.9 0.6 44.7 93 1

0 0 17 10.1 0 2.9 26 0 16

0

19.0

30.3

16.7

9 (m depth)

0 0 12 2.9 2.9 28.4 14 6

Transect

0 5.7 21.0

0 0.3 I.0

40

0

0

1 0 0 0 0 0

0.5

NSO NS 31 NS 0.3

NS

S

13

2

1.2

NS 41.0

P

25

0

25.5

0 s 0 NS2 1 NS 3.3 NS 1.3NS 47.7 S 11 NS 0 NS

0

21.3

0 7.2 0

0

0

45.3 0 20 0 0 0 3 0

41.6

4.8

6 0.7 2.8

12

7

5.3 0 5 1.8 0.1 iO.8 15 43

62.6

4 0 10 2.4 10.2

4 0 3.5 5-5

2.0 o 9 7.2 0 7.0 17 2

6.3 0 15 9.5 3.8 30.6 9 0 0

37.2

13.9

Transect

1.4 0

8

12

0.4 11 2 6.9 0.2 29.6 31 0

7.3

15.7

16 5.7 21.8

7

12

1 13.5 1.1 22.8 71 0

0

2.4

18.8

depth) (m .______.

10

for Casco Island transects

16.2

12.7

interval

12.7

(D) per 2177 cm? for each depth (letters as in Table 1)

0 0 0 9.6 0.6 32.1 114 0

TABLE 3. Mean percentage coverage (C) or total density and inorganic categories, based on photographic analysis.

0 0

41

30

0 o o 15.3 ‘1.7 31.5 93 0

0

19.8

0 0 15

2 2.2 0

45

3

20 4

0 o o 4.3 1.9 50.4 64 o

0.1

25.6

0 o 0 15.5 0.7 21.1 26 2

0.1

22.0

k

S

NS NS NS S NS NS

NS NS

NS

NSHS NS NS NSNS NSNS NSNS HSHS NS HS NS NS

S NS

P

4 5

9 and 10 for major organic

Depth zonation of sublittoral epibenthos

581 -.

‘..1 0 ‘.., I,-..

0

2

4

6

0

IO

12 Depth

14

I

I

16

10

“..I.., I I +.I . . ..I .I.. ,. _ 20

22

24

26

28

30

(m)

Figure 3. Plot of density per m* of Srrongylocenr~otus droebachiensis with increasing depth at (a) Simpson Island, (b) Casco Island and (c) Spruce Island. (Mean values and standard deviations for all transects at each locality.)

yield either percentage coverage or density values for biota, bare rock and sediment; or on counts from two 1 m* quadrats per segment to yield mean density values per rnz for larger individual organisms.The photo-transect data are shown for each locality in Tables l-3. General organic and inorganic categories: Biotic coverage, particularly by encrusting organisms, was high, generally ranging between 60 and 90% of the available primary substrate area while uncolonized bare rock was virtually absent, except in the shallowest parts of the transects. Sediment cover occurred mainly in pockets or at the baseof ledges and increased gradually with depth, reaching 100%at the lowest limit of the transects, where hard substratesdisappeared. Crwtose coralline algae: Crustose coralline algae were the most important biotic components, in terms of coverage, at all localities at depths lessthan 14 m, except on vertical cliff faces, where light, the major factor thought to influence coralline algae depth distribution (Adey & Macintyre, 1973) is reduced. While the pattern of distribution along individual transects was somewhatvariable, linear regressionsof algal coverage on depth for all transects combined showed a highly significant negative correlation (PC 0.002). In this study individual species could not be separated, but the most common species in the Gulf of Maine area are Clathromorphum circumscriptum, C. compactum, Lithophyllum orbiculatum and Phymatolithon rugulosum (Adey, 1964, 1965, 1966a,b). While there is a general reduction in coverage below about 14 m depth in the Deer Island region it is clear that crustose coralline algae can survive to the baseof the circalittoral zone (sensuPeres, 1967a,b) in other regions (Sears & Cooper, 1978; Lewbel et al., 1981). Bottom photographs of 0.25 m2area from Head Harbour Passage,between Deer Island and Campobello Island, show no crustose coralline algae on hard substrates below 32 m (Logan, unpublished) but Harris et al. (1979) noted the gradual disappearanceof crustose coralline algae between 33 and 42 m depth in the Gulf of Maine, where waters are clearer. At the lower depth limits of crustose coralline algae, light values usually approximate to 0.05-0.01% of surface irradiance (Luning & Dring, 1979). Petrocelis middendorfii: This encrusting non-coralline red alga was the second most abundant category recognized in terms of coverage. At Spruce and Casco Islands a trend of decreasing coverage with increasing depth was apparent (Tables 2, 3) which again is thought to be strongly influenced by diminishing light levels.

582

A. Logan, F. H. Page t3 M. L. H. Thomas

TABLE 4. Species, species groups and inorganic depth distribution (presence/absence)

Algae: Crustose coralline algae Petrocelis middendorfi Red filamentous alga # 1 Red filamentous alga # 2 Red filamentous alga # 3 Porifera: Iophon paaersoni Haliclona sp. Unidentified sponges

Mid-depth

Cluster A

Cluster B

Clifffaces cluster

X X X X X

X X

Annelida: Spirorbis borealis Potamilla renformis Myxicola infundibulum Terebellidae Mollusca: Tonicella spp. Acmaea testudinalis Sdariella obscura Margarites helicinus Buccinum undatum Coryphella rujibranchialis Volsella modiolus Anomia sp. Bryozoa: Dendrobeania murrayana Caberea ellisii Unidentified encrusting Brachiopoda: Terebratulina

X

# 1-9

Coelenterata: Tubularia spectabilis Campanularia sp. Se&aria spp. Pennaria tiarella Unidentified hydroids Gersemia rubiformis Tealia felina Metridium senile Gmactinia sp.

Chordata: Lktaplia clavaraAmaroucium spitzbergense Didemnum albidum

analysis

Upwardfaces cluster

X X X X X

X X X X X

X X X

X X

X X X

X X X

X X X X X X X X X X X X X

X

X

X

X

X X

X X X

X X X

X X X X

X X X

X X

X X X X X X X

Deep zone cluster

X X X X X

X X X X X X X X X

X X

and their

zone

X X X X

X X X X X X X

X

X X X X X X X X

X X

X X X

X X X

X

X

X

X

X X

X X X

X

septentrionalis

Ekhinodermata: Henricia sp. Aaerias sp. @hiopholis aculeaza Strongylocentrotus droebachiensrs

used in cluster

zone

Shallow

Category

groups

X X X X X X

X X

X X

X

X

X

X

X

X

X Y

X

X X

X X

X X

Depth zonation of sublittoral epibenthos

TABLE

583

--

&-continued

Shallow zone

Mid-depth

zone

Cluster A

Category Lhdrodoa

Sediment-hydroid-bryozoan association Volsellamodiolusvalves Bare rock Sediment

Clifffaces cluster X

carnea

Bolteniaovifera Bolteniaechinata Halocynthiapyniformis Others:

Total

Cluster B

X

Upwardfaces cluster

Deep zone cluster

X

X

X X X

X X X

X

X X X

X

X

X

X

X

X

X

X

X

25

22

36

42

47

Acmaea testudinalis: This grazing species is the only common limpet in the area, but it was rare at Casco Island. Although variance was great, there was a general decrease in numbers of individuals with increasing depth which was highly significant at Spruce Island (Table 2). Chitons: The grazing species Tonicella murmorea and T. rubra are common in the Deer Island sublittoral zone but could not be separated in the photographs. At all localities density of chitons increased to about 13 m depth, then decreased at greater depths at Spruce and Casco. Hydroids: Tubularian, sertularian, pennarian and campanularian hydroids were recognized, but each category was present in such low quantities that only total hydroid cover has been considered here. Hydroids were most abundant at Spruce and Casco Islands but showed no significant trends with depth at these localities. Bryozoans: Caberea ellisii and Dendrobeania murrayana were the only bryozoans encountered. Coverage values for the combined species were low and showed no significant trends with depth. Sponges: Identification to species level of sponges from photographs was difficult, given the prevailing state of taxonomy of eastern Atlantic sponges, therefore they were treated as a group. At all three localities sponges were virtually absent above 4 m depth; below this depth sponges increased significantly with depth, particularly at Casco Island (Table 3) and also at all stations combined (P
A. Logan, F. H. Page & M. L. H. Thomas

584

TABLE 5. Mean abundance and species richness (standard error in parentheses) of biota, bare rock and sediment within each depth zone (from all transects combined) defined by cluster analysis. D = density per 2177 cm* Shallow Cluster A (n=9) (Dm=5.3)

Category Crustose

Red filamentous Red tiamentous Red filamentous

C C C

0.0

(0.1)

0.0

(0.0)

0.1

(O-4)

0.2 0.6

(0.6) (0.5)

0.0 0.2

(0.0) (0.8)

2.2 1.2

(3.8) (1.6)

D’ D D’

1.2 (3.8)1 0.0 (0.0) 0.0 (0.0)’

0.1 0.0 0.0

(0.0)x (0.0) (0.0)2

0.0 (O.O)j 0.0 (0.0) 0.0 (O-O),

0.3

(1.2) (50,4)* (0.0)

G. rt4b@r?zi~ Total bryozoans Total hydroids Total sponges Bare rock Sediment

C C

Volsella)

B. undoturn A. testudinalis

T. felina

Mean diversity (Species richness)

(Dm=8.2m)

alga # 1 alga # 2 alga # 3

2.0 69.5 0.0 0.0 0.0 0.1 0.1 10.0 4.9 0.1 0.0 0.8 0.0 0.0 0.0

chitons (Tonicella M. infundibtdum Gonactinia sp. M. senile

(n==13)

49.9 28.4

D D’ D D D D D D D D D D’ D’ D C C C

spp.)

(3.3) (38.6)’ (0.0) (0.0) (0.0) (0.3) (0.3) (8.3) (4.3) (0.3) (0.0) (2.2)r (O.O)l (0.0) (0.0)

73.2 0.0

(25-8) (19.3)

Cliff-faces

C C

H. pyr&wmis B. echinata B. omfera D. clavata & A. spitzbergense S. droebachiensis Henrikia sp. T septentknalis Mussels (Myrilus, C. rufibranchialis

Cluster B (n=lZ) (Dm=4,5m) 58-O 18.3

Mid-depth

-

Algae

Coralline

P. mtddendorji

(15.4) (15.7)

zone

30.8 22.0

8.9

(17.1) (17.1)

(10.3)

zone Upward-faces (n= 16) (Dm=11.5m)

39.6 20.0

Deep zone _____~~ ~(n= 14) (Dm=18.4m) __..~

(16.3) (23.1)

7.6 2.5

1.1

(1.2)

0.3 3.1

(0.7) (5.0)

1.0 (3.4) 0.1 (0.2) 0.1 (0.4)

6.4

(8.7)r (0.6) (13.1)'

4.6 14.7

(3.7) (14.5)'

3.5

(5.7)

41.8

(38.0)

(41.5)+

32.9

(16.1)3

42.8

(0.9) (35.4)

0.3 0.4

0.0

(0.0)

0.5 34.7

0.0

(0.0)

0.0

(0.0)

0.0

(1.0) (0.0)

0.2 0.1 7.5 4.3

(0.6) (0.3) (8.4) (6.3)

0.0 O-2 6.8 13.1

(0.0) (O-6) (6.2) (6-8)

2.6 0.8 4.8 17.8

(2.6) (1.7) (7.0) (8.0)

0.1

(0.3)

6.1

(4-8)

0.2

(0.6)

60.8

0.0

(O.O)a

1.0 (2,5)5

(31.9)’

(0.6)

1.7

16.4

(15.1) (13.2) (8.8) (3.7) (8.0) (2.6) (13.6) (0.2)' (4.8)5 (1.2) (4.2) (7.2) (14.8)

0.0

(O.O)Z

0.0

(0.0)s

0.4

0.0 0.0

(0.0) (0.0)

0.0

(0.0)

3.1

(0.2)4 (1,1)4 (8.6)

(2-l) (0.7) (5-3)

0.3 5.3 4.7

(0.6) (5.6) (5.4)

7.6 15.0 2.4 0.4 5.3 1.6 5.8 0.0 4.3 0.4 3.8 IO.2 30.1

5.9

(9.8) (7.7)

0.2 9.2

24.2

1.6 (3.6)

(75.2)

5.8

(13.2)

(8.2)1

0.0

-

(1.4)

(1.1)

0.3

(0.4)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

2.0 0.5 4.9

7.4 3.8

(9.6) (5.0)

13.0 2.0

(12.7) (3.8)

1.2 26.4

(1-4) (10.5)

1.2 10.4

(1.5) (6.5)

2.5 13.7

(2.8) (9.6)

12.7

(1.8)

8.2

(2-4)

21.0

(2.6)

22.8

(3-9)

38.5

(4.5)

D = density per 2177 cm*; D1 = density per mZ; C = percentage cover; 1 = sample number (n) of 19; 2 = n of 24; 3 = n of 15; 4 = n of 28; 5 = n of 14. Dm = mean depth, in metres, below MLW. For abbreviations to species names, see Table 4.

rujibranchialis: This is the only nudibranch common subtidally in the area and was particularly abundant at CascoIsland, where densitiesincreasedmarkedly with depth (Table 3). Nudibranchs generally are carnivorous, and in many speciesthe colour of the cerata is determined by that of the prey species(Zinn, 1975). Usually the prey is a species of hydroid or anemone (Gosner, 1979) and there is a positive correlation between the density of C. rufbranchialis and the percentage coverage of hydroids (PC 0.01). The orange-red colour of the cerata strongly. suggeststhat one of the prey speciesis the red hydroid Tubularia spectabilis. Terebratulina septentrionalis: The life habits, distribution and population structure of this brachiopod have been studied extensively by Logan and Noble (1971), Logan et al. (1975), Webb et al. (1976), Noble et aE. (1976), Noble and Logan (1981) and Witman and Coryphella

585

Depth zonation of sublittoral epibenthos

I

Mid-depth zone: king surfaces

Shallow

zone:

Mid-depth Cliff face

Deep

Upword

A

zone:

zone

Figure 4. A dendrogram plot of photographic sample intervals, using Jaccard’s Coefficient of Association, weighted-pair method. Sample stations l-4 from Simpson Island, 5-8 from Spruce Island and 9 and 10 from Casco Island. Sample letters refer to position of sample on transect (see Figure 2, black dots).

Cooper (1983). It was found consistently at Simpson and Casco Islands, but less so at Spruce Island. Maximum densities at Simpson Island corresponded with shadedcliff faces but only one significant depth trend was apparent in the data. This speciesis frequently covered by spongeson cliff faces and this may have resulted in brachiopod abundancebeing underestimated in the photographs. Myxicola infundibtdum: The life habits of this polychaete have been described by MacKay (1977). It was most common at Simpson Island, where highly-cleaved volcanic rocks offer a multitude of cracks and crevices for its attachment. There wasa highly significant increase in abundancewith depth at this locality (Table 1) which is not clearly shown at the other localities. Strongylocentrotus droebachiensis:This sea urchin was abundant everywhere and showed a significant negative regressionof density per m* on depth at all localities (PC 0 .OOl) for Simpsonand CascoIslands and P
586

A. Logan, F. H. Page 0 M. L. H. Thomas

Cluster analysis Binary data (presence/absence) of 55 species, speciesgroups, bare rock and sediment, including only those categoriesin 10%or more of the sampleintervals, were used to produce a cluster analysisof sampleintervals employing the methodology previously described. The speciesinvolved are shownin Table 4, while the meanabundanceand speciesrichness of the most important categories within each depth zone are shown in Table 5. Five major clusters emerged from this analysis(Figure 4), representing three depth zones; a shallow, mid-depth and deep zone. The shallow zone extends from MLW to a mean depth of 5 m and consists of two clusters, A and B, representing minor biological differences associatedwith the presence of hydroids only in cluster A. The zone is alga-dominated, characterized by crustose coralline algae and Petrocelismiddendorji, which together cover over 70% of the primary substrate, imparting a characteristic pink-red colour to this zone. Other macro-algae are rare and patchily distributed, as are bryozoans, while spongesare virtually absent. Species richnessas a whole is low compared to the other zones. The seaurchin Strongylocentrotus droebachiensis,the limpet Acmaea testudinalisand chitons are very common in this zone, but their influence on the community structure in terms of grazing pressure has yet to be evaluated. The mid-depth zone has a mean depth of 10m and comprisestwo clusters, one representing well-illuminated upward-facing surfaces and the other representing shadedcliff faces. The mid-depth zone as a whole is characterized by greater speciesrichness than the shallow zone, greater coverage of sponges, bryozoans and hydroids, lower densities of seaurchins and limpets and lessarea1coverage by encrusting algae.The cliff-face cluster typically showsreduced coverage of crustose coralline algae and hydroids, lower densities of sea urchins, higher densities of bryozoans, anemonesand brachiopods and greater amounts of sediment, particularly at the baseof the cliff faces. The deep zone hasa meandepth of 18 m, which is generally below the 1%level of surface irradiance. Kelp macro-algaeare absent while crustosecoralline algaepersist, though with much reduced coverage. The deep zone is animal-dominated and supports the greatest speciesrichness of organisms, with sponges, hydroids, anemones,brachiopods, colonial and stalked tunicates all important. The attached biota are highly three-dimensional, up to 20 cm above the rock surface, mainly due to large erect and globulose sponges,which cover almost one-third of the primary surface area. Sublittoral zonation Unlike the universally accepted and clearly defined zonation schemesfor the rocky intertidal zone described by Lewis (1964) and Stephensonand Stephenson(1972), the rocky sublittoral zone has yet to be divided into a generally accepted zonation schemewhich is applicable to all coasts. Peres and Molinier (1957) divided the sublittoral zone into infralittoral and circalittoral subzones, the infralittoral subzone extending from ELWS to the lower limit of photophilous macro-algae, corresponding approximately to the 1% surface irradiance level (Peres, 1967a), while the circalittoral subzone extends from the lower boundary of the infralittoral subzoneto the lower limit of growth of sciaphilousalgae, such as Melobesidae. This scheme,later described in more detail by Peres (1967a, b) was first described for the Mediterranean Sea but has recently been adapted for use in the North Atlantic by Hiscock and Mitchell (1980). They re-evaluated the subzonesinfralittoral and circalittoral, and divided both into upper and lower units, basedon the presenceor absence of certain algae. In the Deer Island area the paucity of kelps, particularly laminariales,

2

s 9w

Peres and Molinier (1957)

6.

General

zonation

infralittoral

circalittoral

Upper

infralittoral

Lower

Upper

Hiscock and Mitchell (1980) (subzone divisions)

TABLE

zone

Deep zone

Mid-depth

zone

Shallow

5; *3 83 E:8 3Q

B

A

epibenthic

(this study)

sublittoral

Clusters

scheme for shallow

18

10

5

communities

in Deer

surfaces

All rock surfaces

Sub-boulder

Steeply-inclined surfaces and cliff faces ____ ---_-______ -___

Upward-facing and gentlyinclined rock surfaces

Community designation

Bay of Fundy,

Canada

T. septentrionalis community

T. septenttinalis community

T. septentrionalis community

Encrusting algae-urchin community

Encrusting algae-urchin community Terebratulina septentrionaiis community

Island region,

facing and inclined rock surfaces Sub-boulder surfaces

Upward

Substratum colonized

on hard substrates

I

588

A. Logan, F. H. Page & M. L. H. Thomas

makes comparison with the general zonation schemedifficult. However, scattered kelps do occur in the shallow zone, indicating it as upper infralittoral, while the total absence of kelps in the mid-depth zone suggeststhat it belongsin the lower infralittoral of Hiscock and Mitchell (1980). The deep zone lies below the level of 1%surface irradiance and photophilous macro-algae distribution, hence defining the infralittoral boundary. It is therefore wholly within the upper circalittoral of Peres (1967~). The results of this study and that by Noble et al. (1976) suggest a general zonation schemefor all rocky sublittoral communitiesin the Deer Island region of the Bay of Fundy (Table 6). All upper and inclined rock surfaces in the shallow zone receive enough light to support the alga-dominated community, the encrusting algae-urchin community. This designation includes both coralline and non-coralline encrusting red algae, as well as Stronglyocentrotus droebachiensis,and the naming of this community follows the general guidelines outlined by Thorson (1957) and Hiscock and Mitchell (1980). Sub-boulder surfaces in the shallow zone, however, support an animal-dominated community named the Terebratulina septentrionaliscommunity by Noble et al. (1976). In the mid-depth zone this cryptic community persistsbeneath boulders, while a facies of it also colonizes shaded cliff faces and steeply-inclined rock surfaces (the rock face subcommunity of Noble et al., 1976). Upper surfaces in this zone still receive enough light to support the encrusting algae-urchin community however. In the deep zone all surfaces are colonized by the gradually emerging T. septentrionaliscommunity. The lower limit of this community is not known, but 0.25 m* area photographs down to 150m depth in Head Harbour Passage (Logan, unpublished) indicate a community dominated by Volsella modiolusand Tealia felina at greater depths. Study of this deeper community is in progress. It is premature at this stageto speculateon the major physical and biological controlling factors of the depth zonation; further studies are needed on physical conditions and on competition, predation and grazing habits of major species.Physical factors, such as wave action and current strength, are apparently only of minor importance in this area. However, light is probably very important in controlling depth zonation of the algae. Noble et al. (1976) found a similar depth zonation of the T. septentrionaliscommunity from sub-boulder surfaces, basedon a cluster analysisof forty samplesfrom four transects. They obtained four clusters grouped as follows: a deep zone, a mid-depth zone, and two shallow zones which are possibly separableon the basisof water energy. Comparisonswith other regions In many regions of the world shallow sublittoral zones are characterized by extensive growth of macro-algae, particularly kelps. Such kelp-dominated communities, with a zonation pattern similar to that described by Lewis (1964) for European coastlines, have been described for eastern North American coastsby Mann (1972) and Boden (1979). In the latter region a shallow zone of Alaria sp. and Laminaria di’tata is typically followed by a zone of L. longicruris (or L. saccharina), then a deeper zone of Agarum cribrosum. All these speciesoccur patchily in the Deer Island region, but extensive kelp beds are absent (Neish, 1973a). Previous studies along the Atlantic coastline of Nova Scotia (Breen & Mann, 1976a,b; Mann, 1977; Breen, 1980; Bernstein et al., 1983) have documented the progressive destruction of kelp beds since 1968 by the grazing of the sea urchin Stongylocentrotus droebachiensis. The community resulting from this destruction is one dominated by encrusting algae, with low relative abundanceand diversity of animal macrobenthos.Conceivably therefore, the encrusting algae-urchin community of the Deer Island region, dominated

Depth

zonation

of sublittoral

epibenthos

589

by corallines, may be the result of long-term seaurchin grazing, sincethese algaeare prominent members of the understorey of a kelp bed (Edelstein et al., 1969; Norton et al., 1977; Breen, 1980). Removal experiments with seaurchins, similar to those carried out by Jones and Kain (1967) for the eastern Atlantic, Himmelman et al. (1983) for the St. Lawrence Estuary of the Western Atlantic and Dayton (1975) for the Pacific coast, need to be initiated in the Bay of Fundy area. Harris (1981) has begun such studies in the Gulf of Maine while Larson et al. (1980) have investigated the feeding and nutritional ecology of S. droebachiensisfrom the sameregion, concluding that fleshy algae such as Lam&aria longicruris and Chondruscrispusform an important diet source. The establishmentof kelp and other macro-algaemay also be prevented or retarded by grazing of low densities of molluscs such as limpets and chitons. In the Deer Island area, densities of these organismsin the shallow sublittoral zone averaged between 50 and 70 individuals per m* (Table 5); similar densities have been shown to inhibit the growth of macro-algae in the intertidal zone in other regions (Southward, 1964; Southward & Southward, 1978; Underwood, 1980). A further question concerns the maintenance of urchin populations, in the absenceof their preferred algal food, in the Deer Island area. Douglas (1976) has suggestedthat Strongylocentrotuspurpuratus, under similar conditions on the west coast, may feed on algae washed from the intertidal zone. This may occur here but observations have not shown much drift algae in the environments; it appearsto accumulate in quieter, deeper waters. This matter is unresolved and needsfurther study.

Acknowledgements We acknowledge field assistancefrom Michael Beattie and the crew of R/V Mary 0. The study was supported by N.S.E.R.C. Operating Grants A 4331 and A 6389 to A. Logan and M. L. H. Thomas, respectively.

References Adey, Adey, Adey,

W. H. 1964 The genus Phymatolithon in the Gulf of Maine. Hydrobiologia 24, 377-420. W. H. 1965 The genus Clathromorphum (Corallinaceae) in the Gulf of Maine. Hydrobiologia 26, 539-573. W. H. 1966a The genus Pseudolithophyllum (Corallinaceae) in the Gulf of Maine. Hydrobiologa 27, 479-497. Adey, W. H. 1966b The general Lithothamnium, Leptophytum (nav. gen.) and Phymatoitthon in the GulfofMaine. Hydrobiologia 28, 321-370. Adey, W. H. & Macintyre, I. G. 1973 Crustose coralline algae: a re-evaluation in the geological sciences. Bulletin of the Geological Society of America 84, 883-904. Alcock, F. J. 1946 Campobello, New Brunswick. In Geological Survey of Canada Map 964a (with descriptive notes). Bailey, W. B., Macgregor, D. G. & Hachey, H. B. 1954 AMU~ variations of temperature and salinity in the Bay of Fundy. Journal ojthe Fisheries Research Board of Canada 11, 3247. Bernstein, B. B., Schroeter, S. C. & Mann, K. H. 1983 Sea urchin (Strongylocentrotus droebachienszs) aggregating behavior investigated by a subtidal multifactorial experiment. Canadian Journal of Fisheries and Aquatrr Science 40, 1975-1986. Boden, G. T. 1979 The effect of depth on summer growth of Laminaria saccharina (Phaeophyta, Laminarialesj. Phycologia 18, 405-408. Bohnsack, J. A. 1979 Photographic quantitative sampling of hard-bottom benthic communities. Bulletin of Marine Science 29, 242-252. Bonham-Carter, G. R. 1967 Fortran IV program for Q-mode cluster analysis of nonquantitative data using IBM 7090/7094 computers. Computer Contribution 17, State Geological Survey, University of Kansas, 29 pp. Boudouresque, C. F. 1974 Aire minima et peuplements algaux marins. Bulletin Societt Phycologie de France 19, 141-157.

A. Logan,

590

F. H. Page

& M.

L. H.

Thomas

Breen, P. A. 1980 Relations among lobster, sea urchins and kelp in Nova Scotia. In Proceedings of the workshop on the relationship between sea urchin grazing and commercial-plant harvesting (Pringle, J. D., Sharp, G. J. & Caddy, J. F., eds). Canadian Technical Report, Fisheries & Aquatic Sciences 954, 24-32. Breen, P. A. & Mann, K. H. 1976a Destructive grazing of kelp by sea urchins in eastern Canada. Journal of the Fisheries Research Board of Canada 33, 1278-1283. Breen, I’. A. & Mann, K. H. 19766 Changing lobster abundance and the destruction of kelp beds by sea urchins. Marine Biology 34, 137-142. Chapman, A. R. 0. 1981 Stability of sea urchin dominated barren grounds following destructive grazing of kelp in St. Margaret’s Bay, eastern Canada. Marine Biology 62, 307-311. Chardy, P. 1970 Ecologic des crustaces peracarides des fonds rocheux de Banyuls-sur-Mer. Amphipodes, Isopodes, Tanaidaces, Cumaces, infra- et circa-littoraux. Vie et Milieu 21, 657-720. Dayton, P. K. 1975 Experimental evaluation of ecological dominance in a rocky intertidal algal community. Ecological Monographs 45, 137-159. Dayton, P. K., Robilliard, G. A. & Paine, R. T. 1970 Benthic fauna1 zonation as a result of anchor ice at McMurdo Sound, Antarctica. In Antarctic Ecology, Vol. 1. Academic Press, New York, pp. 244-258. Dayton, P. K., Robilliard, G. A., Paine, R. T. & Dayton, L. B. 1974 Biological accommodation in the benthic community at McMurdo Sound, Antarctica. Ecological Monographs 44, 105-128. Douglas, C. A. 1976 Availability of drift materials and the covering response of the sea urchin Strongylocentrotus purpuratus (Stimpson). Pacific Science 30,83-89. Edelstein, T., Chen, L. & McLachlan, J. 1969 Preliminary survey of the sublittoral flora of Halifax County. Journal of the Fisheries Research Board of Canada 26, 2703-27 13. Forrester, W. D. 1960 Current measurements in Passamaquoddy Bay and the Bay of Fundy, 1957 and 1958. Journal of the Fisheries Research Board of Canada 17,727-729. Gaskin, D. E., Smith, G. J. D. & Van Ness, B. 1979 Environmental conditions in Head Harbour Passage and vicinity, New Brunswick, Canada, with special reference to visibility and some local water movements. Report National Marine and Fisheries Service 46 pp. Gosner, K. L. 1979 A Field Guide to the Atlantic Seashore. Houghton Mifflin Company, Boston, 329 pp. Grange, K. R., Singleton, R. J., Richardson, J. R., Hill, I’. J. & Main, W. deL. 1981 Shallow rock-wall biological associations of some southern fiords of New Zealand. New Zealand Journal of Zoology 8, 209-227. Gulliksen, B. 1974 Marine investigations at Jan Mayen in 1972. Det. Kgl. Norske Videnskabers Selskab Museet, Miscellanea 19,46 pp. Gulliksen, B. 1977 Studies from the “UWL Helgoland” on the macrobenthic fauna of rocks and boulders in Lubeck Bay (western Baltic Sea). Helgolander wissenschaftliche Meeresunterssuchungen 30, 519-526. Gulliksen, B. 1978 Rocky bottom fauna in a submarine gulley at Loppkalven, Finnmark, Northern Norway. Estuarine and Coastal Marine Science 7,361-372. Harris, L. G. 1981 Studies of community succession in an urchin barrens area following sea urchin removal. Abstracts, American Zoologist 21, 1019. Harris, L. G., Hulbert, A., Witman, J. D., McCarthy, K. & Pecci, K. 1979 A comparison by depth and substrate angle of subtidal benthic communities at Pigeon Hill in the Gulf of Maine. Abstracts, American Zoologtst 19,

1010.

Himmelman, J. H., Cardinal, A. & Bourget, E. 1983 Community development following removal of urchins, Strongylocentrotus droebachiensis, from the rocky subtidal zone of the St. Lawrence Estuary, eastern Canada. Oecologia 59, 27-39. Hiscock, K. & Hoare, R. 1975 The ecology of sublittoral communities at Abereiddy Quarry, Pembrokeshire. Journal of the Marine Biological Association of the United Kingdom 55, 833-864. Hiscock, K. & Mitchell, R. 1980 The description and classification of sublittoral epibenthic ecosystems. In The Shore Environment, 2: Ecosystems (Price, J. H., Irvine, D. E. G. & Farnham, W. F., eds). Systematics Association Special Volume 17(a), Academic Press, London and New York, pp. 323-370. Hoare, R. & Peattie, M. E. 1979 The sublittoral ecology of the Menai Strait. I Temporal and spatial variation in the fauna and flora along a transect. Estuarine and Coastal Marine Science 9, 663-675. Hulbert, A. W., Harris, L. G. & Witman, J. D. 1980. Subtidal community zones on hard substrate in the Gulf of Maine. Abstracts, American Zoologist 20, 883. Jansson, A. M. & Kautsky, N. 1977 Quantitative survey of hard-bottom communities in a Baltic Archipelago. In Biology of Benthic Organisms, pp. 359-365 (Keegan, B. F., Ceidigh, P. 0. & Boaden, I’. S. J., eds). 1 lth European Symposium on Marine Biology, Galway, 1976. Pergammon Press, Oxford 630 pp. Jones, N. S. & Kain, J. M. 1967 Subtidal algal colonization following the removal of Echinus. Helgolander wissenschaftliche Meeresunterssuchungen 15, 460-466. Knight-Jones, E. W. & Nelson-Smith, A. 1977 Sublittoral transects m the Menai Straits and Milford Haven. In Biology of Benthic Organisms, pp. 379-389 (Keegan, B. F., Ceidigh, I’. 0. & Boaden, P. J. S., eds). 11th European Symposium on Marine Biology, Galway, 1976. Pergammon Press, Oxford, 630 p. Larson, B. R., Vadas, R. L. & Keser, M. 1980 Feeding and nutritional ecology of the sea-urchin Strongylocentrotus droebachiensis in Maine, U.S.A. Marine Biology 59,49-62. Lewbel, G. S., Wolfson, A., Gerrodette, T., Lippmcott, W. H., Wilson, J. L. & Littler, M. M. 1981 Shallow-water benthic communities on California’s outer continental shelf. Marine Ecology (Progress Series) 4, 159-168.

Depth

zonation

of sublittoral

epibenthos

591

Lewis, J. R. 1964 7% Ecology of Rocky Shores. The English Universities Press Ltd, London, 323 pp. Logan, A. 1979 The Recent Brachiopoda of the Mediterranean Sea. Bulletin de l’lnstitut oceunogruphique, Monaco 72, 112 pp. Logan, A. & Noble, J. I’. A. 1971 A Recent shallow-water brachiopod communny from the Bay of.Fundy. Marittme Sediments 7,85-9 1. Logan, A., Noble, J. I’. A. &Webb, G. R. 1975 An unusual attachment of a Recent brachiopod, Bay of Fundy, Canada. Journal of Paleontology, 49, 557-558. Logan, A., MacKay, A. A. & Noble, J. I’. A. 1983 Sublittoral hard substrates. In Marine and Coastal Systems of the Qnoddy Region. New Brunswick, pp. 119-139 (Thomas, M. L. H., ed.). Canadian Specrul Pnbl&tion of Fisheries & Aquatic Sciences 64, 306 pp. Lundalv, T. 1971 Quantitative studies on rocky-bottom biocoenoses by underwater photogrammetry. Thulussa Jngosluvica 7, 201-208. Luning, K. & Dring, M. J. 1979 Continuous underwater light measurement near Helgoland (North Sea) and its significance for characteristic light limits in the sublittoral region. Helgoliinder wissenfschuftliche Meeresunterssuchungen 32, 403424. MacKay, A. A. 1977 Myxicolu infundibufum. I: Ecology in the Bay of Fundy. Report to Research and Development Brunch, N. B. Department of Fisheries. 23 pp. MacKay, A. A. 1978~ Bay of Fundy Resource Inventory. St. Croix River Passamaquoddy Bay. Marine Research Associates Ltd, Report to N.B. Department of Fisheries, 219 pp. MacKay, A. A. 19786 Bay of Fundy Resource Inventory. Back Bay-Letite Inlet, Marine Research Associates Ltd, Report to N. B. Department of Fisheries, 134 pp. MacKay, A. A. 1978c Bay of Fundy Resource Inventory. Deer Island-Campobello Island. Marine Research Associates Ltd, Report to N. B. Department of Fisheries, 223 pp. MacKay A. A. 1979 Bay of Fundy Resource Inventory. The Grand Manan Archipelago. Marine Research Associutes Ltd, Report to N. B. Department of Fisheries, 141 pp. Mann, K. H. 1972 Ecological energetics of the seaweed zone in a marine bay on the Atlantic Coast of Canada. I. Zonation and biomass of seaweeds. Marine Bio!ogy 12, I-10. Mann, K. H. 1977 Destruction of kelp beds by sea-urchins: a cyclical phenomenon or irreversible degradation? Helgolander wtssenschuftiche Meeresunterssuchungen 30, 455-467. Muus, B. J. 1968 A field method for measuring exposure by means of plaster balls: a preliminary account. Sarsia 34, 61-68. Neish, I. C. 1973a The distribution of kelp and other commercially useful marine algae in Charlotte County, New Brunswrck. Applied Murrne Research Ltd, Report to N. B. Department of Fisheries, 46 pp. Neish, I. C. 1973b The distribution of sea urchins in Charlotre County, New Brunswick. Applied Marine Research Ltd, Report to N. B. Department of Fishertes, 22 pp. Noble, J. I’. A. & Logan, A. 1981 Size-frequency distributions and taphonomy of brachiopods: a Recent model. Pulaeogeogruphy, Palueoclimatology, Palueoecology 36, 87-105. Noble, J. I’. A., Logan, A. & Webb, G. R. 1976 The Recent Terebrutulinu Community in the rocky subtidal zone of the Bay of Fundy, Canada. Lethaiu 9, 1-17. Norton, T. A., Hiscock, K. H. & Kitching, J. A. 1977 The ecology of Lough Ine. XX. The Laminurzu forest at Carrigathorna. Journal of Ecology 65, 91%941. Osman, R. W. 1977 The establishment and development of a marine epifaunal community. Ecologicul Monographs 47, 37-63. Peres, J-M. 1967~ Les biocoenoses benthiques dans la systeme phytal. Recueil des Truvuux de la Station Martne d’Endoume 58, 3-l 13. Peres, J-M. 19676 The Mediterranean benthos. Oceanography and Marine Biology Annual Review 5,449-533. Peres, J-M. & Molinier, R. 1957 Compte-rendu du colloque tenu a Genes par la comite du benthos de la Commission Internationale pour 1’Exploration Scientifique de la Mer Mediterranee. Recueil des Truvuus de la Station Marine d’Endoume 22, 5-l 5. Scheaffer, R. L., Mendenhall, W. & Ox, L. 1979. Elementary Survey Sampling. Duxbury Press, Massachusetts, 278 pp. Sears, J. R. & Cooper, R. A. 1978 Descriptive ecology of offshore, deep-water, benthic algae in the temperate western North Atlantic. Oceanography and Marine Biology 44, 309-314. Sears, J. R. & Wilce, R. T. 1975 Sublittoral benthic marine algae of southern Cape Cod and adjacent islands: seasonal periodicity, associations, diversity and florisric composition. Ecological Monographs 44, 337-365. Southward, A. J. 1964 Limpet grazing and the control of vegetation on rocky shores. In Grazing in Terrestrial and Marine Environments (Crisp, D. J., ed.). Symposium of British Ecological Society, Bangor, Wales, 1962. Blackwell Scientific Publications, Oxford, U. K., pp. 265-273. Southward, A. J. & Southward, E. C. 1978 Recolonization of rocky shores in Cornwall after use of toxic dispersants to clean up the Torrey Canyon spill. Journal of the Fisheries Research Board of Canada 35, 682-706. Sokal, R. R. & Sneath, P. H. A. 1963 Principles of Numerical Taxonomy. W. H. Freeman & Company, London St San Francisco, 359 pp. Stephenson, T. A. & Stephenson, A. 1972 Life Between Tidemarks on Rocky Shores. W. H. Freeman & Company, L.ondon & San Francisco, 425 pp.

592

A. Logan, F. H. Page & M. L. H. Thomas

Thomas, M. L. H. 1983~ Introduction. In Marine and Coastal Systems of the Quoddy Region, New Brunszoick, pp. l-4 (Thomas, M. L. H., ed.). Canadian Special Publication of Fisheries and Aquatic Sciences 64, 306 pp. Thomas, M. L. H. 1983b Meteorology. In Marine and Coastal Systems of the Quoddy Region, New Brunswick, pp. 5-8 (Thomas, M. L. H., ed.). Canadian Special Publication of Fisheries and Aquatic Sciences 64, 306 pp. Thomas, M. L. H. (in press) Mangrove systems. In Bermuda-Anatomy of an Oceanic Island (Sterrer, W. E., ed.). Wiley Interscience, New York. Thomas, M. L. H., Arnold, D. C. &Taylor, A. R. A. 1983 Rocky Intertidal Communities. In Marine and Coastal Systems of the Quoddy Region, New Brunswick, pp. 39-73 (Thomas, M. L. H., ed.). Canadian Special Pubiication of Fisheries and Aquatic Sciences 64, 306 pp. Thorson, G. 1957 Bottom communities. In Treatise on Marine Ecology and Paleoecology. 1: Ecology (Hedgpeth, J. W., ed.). Geological Society of America Memoir 67, 461-534. Trites, R. W. & Garrett, C. J. R. 1983 The physical oceanography of the Quoddy region. In Marine and Coastal Systems of the Quoddy Region, New Brunswick, pp. 9-34 (Thomas, M. L. H., ed.). Canadian Special Publication of Fisheries and Aquatic Sciences 64, 306 pp. Underwood, A. J. 1980 The effects of grazing by gastropods and physical factors on the upper limits of distribution of intertidal macroalgae. Oecologia 46, 201-213. Webb, G. R., Logan, A. & Noble, J. P. A. 1976 Occurrence and significance of brooded larvae in a Recent brachiopod, Bay of Fundy, Canada. Journal of Paleontology 50,869-871. Weinberg, S. 1978 The minimal area problem in invertebrate communities of Mediterranean rocky substrata. Marine Biology 49, 33-40. Witman, J, D. &Cooper, R. A. 1983 Disturbance and contrasting patterns of population structure m the branchiopod Terebraztdina septeutrionalis (Couthouy) from two subtidal habitats. Journal of Expertmental Marine Biology and Ecology 73, 57-79. Zinn, D. J. 1975 The Handbook for Beach Strollers from Maine to Cape Hatteras. The Pequot Press, Connecticut, 128 pp.