Changes in the diversity of the populations of gammarid crustaceans in the southern Baltic offshore waters

Gammarid crustaceans are common inhabitants of European shallow brackish waters. In the impoverished Baltic Sea fauna they constitute a major component of the near-shore macrofaunal communities, especially in the phytal zone.

The identification of Baltic species of the genus Gammarus was possible thanks to papers by Segerstråle (1947, 1950, 1959) and Kinne (1954). At the time of publication five species (Gammarus. duebeni, G. locusta, G. oceanicus, G. salinus and G. zaddachi) were recorded from the Baltic Sea, and a sixth species (G. inaequicauda) was later added by Jazdzewski (1970). 

The changes in gammarid crustaceans in the southern Baltic from the 1952 -1998. Red - Gammarus salinus, Black - Gammarus locusta, Blue - Gammarus oceanicus, Purple - Gammarus tigrinus, Green - Gammarus zaddachi, Orange - Obesogammarus crassus, Yellow - Gammarus duebeni, Light blue - Pontogammarus robustoides, White - Gammarus inaequicauda, Pale purple - Dikerogammarus haemobaphes.

In Lithuanian waters, in the oligohaline Curonian Lagoon, two alien Ponto-Caspian gammarid species: Pontogammarus robustoides and Obesogammarus crassus were recorded in the 1960s by Gasjunas (1972). These species were intentionally introduced in 1960 to the Kaunas dam reservoir on the Neman River, which empties to the Curonian Lagoon. 

Jazdzewski (1975) recorded Chaetogammarus ischnus, another Ponto-Caspian gammarid in the mouth of the Vistula River. Although it is thought to have already invaded the Vistula in the 1920s (Jarocki & Demianowicz 1931). Jazdzewski (1976) discovered the Atlantic-boreal species, Chaetogammarus stoerensis, in the southern Baltic. Bulnheim (1976) also recorded another alien gammarid Gammarus tigrinus, which is of North American origin, in the Schlei estuary. It had entered the Baltic Sea basin from the middle course of Werra River in Germany in the 1950s.

New alien gammarids

In the last decade further records of new alien gammarid species in Baltic offshore oligohaline waters have appeared in several papers: Gruszka (1995, 1999) records the occurrence of G. tigrinus and P. robustoides in the Szczecin Lagoon, and Konopacka (1998), Jazdzewski & Konopacka (2000) and Konopacka & Jazdzewski (in press) notes the occurrence of these two species and Dikerogammarus haemobaphes and Obesogammarus crassus in the Vistula Lagoon and old brackish arms of the Vistula. Müller et al. (in press) also recorded Dikerogammarus villosus, the next Ponto-Caspian immigrant, in the Szczecin Lagoon. As a result, in the Baltic proper and its offshore lagoons and estuarine waters, we now have seven species of Gammarus, two species of Chaetogammarus, two species of Dikerogammarus, and one species each of Pontogammarus and Obesogammarus.

Changes in Polish waters

In the Polish waters of the Baltic Sea gammarid populations were comprehensively studied by Jazdzewski (1971, 1973) in the Bay of Puck, with some less detailed data available from the Vistula Lagoon in the papers by Zmudzinski (1957) and Jazdzewski (1975). We therefore have information on the relations between particular gammarid species in these two basins from the 1960s (Bay of Puck) and the 1950s (Vistula Lagoon) with quite recent studies from the Bay of Puck by Jeczmien & Szaniawska (2000), Morawski (unpubl.) and Stos (unpubl.) and in the Vistula Lagoon by Jazdzewski et al. (in press). This has allowed us to compare the present composition of gammarid populations in the Bay of Puck and in the Vistula Lagoon with that occurring several decades ago. In the Bay of Puck we still have only native species, but due to the eutrophication of this basin two more oxyphilous gammarids, G. locusta and G. inaequicauda evidently give way to the more resistant G. zaddachi, G. salinus and G. oceanicus (see figure).

Decline in native species

In the oligohaline waters of the Vistula Lagoon native G. zaddachi is now outcompeted by a much more eurytopic G. duebeni and by alien immigrants of the last decade, especially G. tigrinus, P. robustoides and O. crassus. The freshwater oligohaline species Dikerogammarus haemobaphes occurs in the Vistula Lagoon only in its westernmost, least saline parts.

The data presented in the figure is the summary of the many samples collected along the whole shoreline of the study area and so they do not reflect the local diversity of gammarid populations connected with different ecological conditions (especially salinity) at particular stations.

References

Bulnheim H-P. 1976. Gammarus tigrinus, new element in the fauna of the Baltic estuary of Schlei. Schr. Naturw. Ver. Schlesw.-Holst., 6: 79-84 (in German).

Gasjunas I., 1972. Enrichment of fodder basis of water bodies of Lithuania by acclimatized crustaceans-like organisms from the Caspian Seas complex. In: On the breeding of fish and crustaceans-like organisms in the water bodies of Lithuania. Vilnius P. J.Virbickas (ed.), p57-68 (in Russian).

Gruszka P. 1995. Gammarus tigrinus Sexton, 1939 (Crustacea: Amphipoda) - a new species for Polish fauna in the Oder estuary. In: Przyrodnicze aspekty badania wod estuarium Odry i wod jeziornych wojewodztwa szczecinskiego. Mat. Konf. 7, Uniw. Szczecin, p44 (in Polish).

Gruszka P. 1999. The River Odra Estuary as a Gateway for Alien Species Immigration to the Baltic Sea Basin. Acta hydrochim. hydrobiol., 27: 374-382.

Jarocki J. & Demianowicz A., 1931. On the occurrence of a Ponto-Caspian amphipod Chaetogammarus tenellus (G.O. Sars) in the Vistula River. Bull. Int. Acad. Pol. Sci. Lettr. (Cl. Math. Nat. BII): 513-530 (in German).

Jazdzewski K., 1970. Gammarus inaequicauda Stock in the Baltic Sea (Amphipoda, Gammaridea). Crustaceana, 19: 216-217.

Jazdzewski K., 1971. Ecology of Crustacea Malacostraca in the Bay of Puck. Acta biol. med. Soc. sci. Gedan., 16: 9-77 (in Polish).

Jazdzewski K., 1973. Ecology of gammaridsin the Bay of Puck. Oikos, suppl. 15: 121-126.

Jazdzewski K., 1975. Morphology, taxonomy and distribution in Poland of the gammarids of the genera Gammarus Fabr. and Chaetogammarus Mart. (Crustacea, Amphipoda). Acta Univ. Lodz., Lodz: 185pp (in Polish).

Jazdzewski K., 1976. Notes on the occurrence and ecology of Chaetogammarus stoerensis (Reid, 1938) and Corophium multisetosum Stock, 1952 (Amphipoda) in the Baltic Sea. Crustaceana, Leiden, 30 (1): 33-38.

Jazdzewski K. & Konopacka A., 2000. Immigration history and present distribution of alien crustaceans in Polish waters. In: The biodiversity crisis and Crustacea. Proceedings of the 4th Int. Crustacean Congr., Brill, Leiden, J.C. von Vaupel Klein & F.R.Schram (eds.), Vol. 2, Crustacean Issues, 12: 55-64.

Jazdzewski K., Konopacka A. & Grabowski M., (in press). Four Ponto-Caspian and one American gammarid species (Crustacea, Amphipoda) invading Polish waters. Beaufortia.

Jeczmien W. & Szaniawska A., 2000. Changes in species composition of the genus Gammarus Fabr. in Puck Bay. Oceanologia, 42 (1): 71-87.

Kinne O., 1954. The species of Gammarus in the Gulf of Kiel. Zool. Jb. Syst., 82: 405-424 (in German).

Konopacka A., 1998. Dikerogammarus haemobaphes (Eichwald, 1841) (Crustacea, Amphipoda), a new species in Polish fauna and two other rare amphipods in the Vistula River. Przegl. Zool., 42 (3-4): 211-218 (in Polish).

Konopacka A. & Jazdzewski K., (in press). Obesogammarus crassus (G.O. Sars, 1894) - one more Ponto-Caspian species in Polish waters. Przegl. Zool., (in Polish).

Müller O., Zettler M.L. & Gruszka P., (in press). Distribution and status of Dikerogammarus villosus Sovinsky (Crustacea: Amphipoda) in the middle and the upper part of the River Oder and the adjacent waterways. Lauterbornia (in German).

Segerstråle S.G., 1947. New observations on the distribution and morphology of the amphipod, Gammarus zaddachi sexton, with notes on related species. J. mar. biol. Ass. U.K., 27: 219-244.

Segerstråle S.G., 1950. The amphipods on the coasts of Finland-some facts and problems. Comment. biol., Soc. Sci. Fenn., 10 (14): 1-28.

Segerstråle S.G., 1959. Synopsis of Data on the Crustaceans Gammarus locusta, Gammarus oceanicus, Pontoporeia affinis and Corophium volutator (Amphipoda Gammaridea). Comment. biol., Soc. Sci. Fenn., 20 (5): 3-23.

Zmudzinski L., 1957. Zoobenthos of Vistula Lagoon. Pr. Morsk. Inst. Ryb., 9: 453-500 (in Polish).