Benthic Fauna Assemblages in Batchawana Bay, Lake Superior R.M. Dermott Great Lakes Fisheries Research Branch Canada Centre for Inland Waters 867 Lakeshore Road, PO. Box 5050 Burlington, Ontario L7R 4A6 May, 1984 Canadian Technical Report of Fisheries and Aquatic Sciences 1 No. 1265 Fisheries Peches and Oceans et Oceans Canada Canadian Technical Report of Fisheries and Aquatic Sciences Technical reports contain scientific and technical information that contributes to existing knowledge but which is not normally appropriate for primary literature. Technical reports are directed primarily toward a worldwide audience and have an international distribution. No restriction is placed on subject matter and the series reflects the broad interests and policies of the Department of Fisheries and Oceans, namely, fisheries and aquatic sciences. Technical reports may be cited as full publications. The correct citation appears above the abstract of each report. 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I es rapports epuises seront fournis contre retribution par des agents commerciaux. ti Canadian Technical Report of Fisheries and Aquatic Sciences 1265 BENTHIC FAUNA ASSEMBLAGES IN BATCHAWANA BAY, LAKE SUPERIOR by Ronald M. Dermott Great Lakes Fisheries Research Branch Fisheries and Oceans Canada Canada Centre for Inland Waters P.O. Box 5050 ~urlington, Ontario L7R 4A6 ii c Minister of Supply and Services Canada 1984 FS 97 - 6 / 1265 ISSN 0706 - 6457 Correct citation for this publication is: DERMOTT) R. M. 1984. Benthic fauna assemblages in Batchawana Bay. Lake Superior. Can. Tech. Rep. Fish. Aquat. Sci. 1265: iii + 17 p. iii ABSTRACT Dermott, R. M. 1984. Benthic fauna assemblages in Batchawana Bay, Lake Superior. Can. Tech. Rep. Fish. Aquat. Sci. 1265: iii + 17 p. The benthic fauna of oligotrophic Batchawana Bay consists of three assemblages dependent on depth and sediment composition. The deep-water fauna is more similar to that of Georgian Bay than that in Lake Superior. As a result of the enclosed nature of the bay, the warm shallows support a fauna more typical of the historical fauna in the now eutrophic embayments of the lower Great Lakes. Key words: macroinvertebrates, community, profundal, sandy shallows, POntoporeia, Hexagenia, Sphaerium, gastropods, oligotrophic. ~ , RESUME Dermott, R. M. 1984. Benthic fauna assemblages in Batchawana Bay, Lake Superior. Can. Tech. Rep. Fish. Aquat. Sci. 1265: iii + 17 p. La faune benthique de la Baie Batchaouna, qui est oligotrophe, est constituee de trois assemblages selon la profondeur et la composition des sediments. La faune d'eau profonde ressemble beaucoup plus a celIe de la Baie Georgienne quIa celIe du Lac Superieur. A cause de la nature fermee de la baie, les hauts-fonds chauds hebergent une faune plus caracteristique de la faune historique dans les baies maintenant eutrophes des Grands Lacs d'aval. Mots clefs: macro-invertebres, communaute, profonde, hauts-fonds sablonneux, Pontoporeia, Hexagenia, Sphaerium, gastropodes, oligotrophe. - 1 - Introduction sites is north of Batchawana Island (grid J7) and DS south of the island The macrobenthic communities of (grid E6). Percent sand and silt, mean inshore areas and embayments of the Great particle size, and organic content of the Lakes have frequently been investigated sediments were analysed following the in relation to cultural enrichment. methods in Thomas ~!l. (1972). Changes in species composition due to reduced water quality have been observed The sediments were washed through a in all the lakes with major changes sieve of 0.18 mm mesh. The retained occurring in Sagin.w Bay (SchDeider et organisms were preserved in ten percent al., 1969), Western Lake Erie (Carr and formalin, while the molluscs were Hiltunen, 1965) and Toronto Harbour preserved in 70 percent alcohol. The (Brinkhurst, 1970). Less common are organi... were identified, enumerated, studies of the benthic fauna in and the wet weights of each taxonomic undisturbed nearshore areas (Hiltunen, group tallied. Dry weight was calculated 1969; Mozley and Winnell, 1975; and Hare from the percent dry weight estimated for and carter, 1977). each taxon. The Oligochaeta and CbiroDOmidae were mounted in balsam for The present study investigated the identification. The nomenclature of fauna of relatively shallow Batchcwana these taxa follows Brinkhurst and Jamieson Bay, eastern Lake Superior. The study (1971), and Oliver et al. (1978). was part of the assessment of contaminant Nomenclature of the~Trusca follows dynamics in the partially enclosed bay. Clark (1973), while that of the remaining Thomas (1966) undertook a larval lamprey taxa follows Holsinger (1972), and Pennak survey of the bay, collecting qualitative (1978). samples of the benthic invertebrates and fish species present. As he did not Hierarchial clustering was undertaken identify the Diptera or Oligochaeta, or on the May samples, using the percentage estimate the relative abundance of the similarity of community (PSc) to obtain a macroinvertebrates, particular attention numeric measure of similarity between the was given to these parameters. 27 sites examined. This was calculated as: Area Description PSc • 100 - 0.5 t 'a - bl The bay is 40 km north of Sault Ste. Marie and is surrounded by heavily where a and b are, for each species, the forested hills (300 m vertical), composed percentages of the total animals from the of Precambrian granitic rocks. The study sites A and B. Diversities of the area has limi ted hUlllan influence. Less commun1t1es were calculated using the than 10 percent of the shore line has Shannon index of diversity: cottage development, primarily along the southeast shore. The majority of the H • - t (Ni/N) In (Ni/N) total contaminants in the bay enters via long-range atmospheric input. where Ni is the abundance of each taxon, N is the total abundance and In is the Maximum depth in the enclosed section natural log. of the bay is 46 m, occurring to the east of Batchawana Island. Much of the bay is RESULTS less than 6 m deep with extensive sand shoals (Fig. 1). As a result, warm Table 1 lists the physical data of surface water accumulates during the depth, percent sand, and organic content summer reaching 17 to 22°C (J. Kelso, of the sediment at the sample sites. The unpublished). Maximum algal biomass was average total dry weight of the 600 mg r (R.. Love, unpublished), which macroinvertebrates at the sample sites classifies the bay as oligotrophic during 1977 is displayed in Figure 2. according to Vollenweider (1968). The greatest biomass (standing stocks) occurred ·at a depth of less than 3 m, Methods along the shoreline and on the sandy shoals south of Batchawana Island. The Duplicate Ponar samples (0.05 m- Z ) lowest occurred in deeper water near the were collected at 27 sites during May and northern inlet to the bay, and along the September 1977 (Fig. 1). Twenty-three of steep, rocky eastern shoreline. these sites followed a universal transverse mercator grid used during a The benthic fauna was readily divided sediment survey of the bay in 1976 (R.. into three major communities dependent on Thomas, unpublished). In addition, two sample depth and substrate. These being: transect lines on the sandy shoals were the profundal species inhabiting t1ne sampled at 3, 3, and 10 m depths, at sediments at depths greater than 20 m, - 2 - those at intermediate depths (5 to 20 m) than the deepwater association, with H on fine sediments with particle size less values ranging from 1.9 to 3.0.