MACROZOOBENTHOS OF THE INTERTIDAL ZONE IN HORNSUND FJORD
Marta BrychczyĹska *
Lech Kotwicki **
* Institute of Oceanography, University of GdaĹsk, ul. PiĹsudskiego 46, Gdynia 81-370
** Institute of Oceanology, Polish Academy of Sciences, ul. PowstaĹcĂłw Warszawy 55, Sopot 81-712
Littoral, or intertidal zone is defined as the area between low and high water marks and constitute a unique marine environment because of regular exposure to the air (Fig. 1.). Strong environmental stress has important impact on the macrofauna living in this area. Except of all factors which influence organisms in littoral zone all around the world, such as: desiccation, wave energy, wide temperature range, fluctuation of salinity, competition for space, communities of tidal range in the Arctic must additionally deal with a half year lasting night, short period of productivity, ice scouring and very low temperature.
Fig. 1.Intertidal zone in Hornsund
The animals retained by a 0,5Â mm mesh size, inhabiting the bottom part of the sea are called macrozoobenthos. They can bury themselves in the soft sediments (infauna), anchor to the hard substrate (sessile organisms), or move around on the bottom (epifauna).
The aim of this study was to find the spatial patterns of macrofauna distribution in sediments in relation to zonation, distance to active glacier (level of inorganic sedimentation, water turbidity, ice-berg scouring intensity), water dynamics (wave energy) and hydrology (water temperature, salinity). Additionally we aim to compare the results of our study with the data collected 20 years ago by Jan Marcin WÄsĹawski and his co-workers. We will verify, if any faunistic changes happened and can be linked to climatic and hydrological changes resulting from a general warming up (increase of mineral sedimentation and fresh water outflow from melting glaciers).
MATERIALS AND METHODS
Material was collected in July 2002 and 2003. Samples were taken at four bays: Isbjornhamna (July, 2002), Stonehehengesteinane - Stone (July, 2003), Adriabukta- Treskelen (July, 2003) and Hyttevika (July, 2003) (Fig. 2.).
Fig. 2. Location of sampling sites
At each bay, during low tide, 9 samples were collected: three at low water mark, three at high water mark, and three in the mid-intertidal zone. 5 cm layer of sediment from a quare (Fig.Â 3.) of 30 x 30 cm were dug out with a spade, sieved on a 0,5 mm mesh size screen and preserved in 4 % formaldehyd solution.
Fig. 3. Strategy of sampling
The species composition, abundance and biomass (wet formalin weight) were determined in the lab. Mollusca were weighed with shells. Dry weight were obtain as 25Â % of wet weight.
A total of 16 taxa of macrofauna were identified: 8 species, 2 genera, 6 higher taxa. The fauna was dominated by oligochaets.
The next most numerous group was juvenile
Gammarus sp. The biomass was dominated by
big amphipods - Gammarus setosus.
Fig. 4. Oligochaeta, a warm living in
Fig. 5. Gammarus setosus easily found on the beach under the stones.
The fauna included also some polychaetes molluscs, bryozoans and hydrozoans. Densities ranged from 33Â ind./m2 in Treskelen at mid-water mark zone to 113Â 733Â ind./m2 in Isbjornhamna at high water mark zone.
The lowest macrofaunal biomass - 0,0003 gÂ d.w./m2 was recorded in Treskelen at mid-water zone. The highest value, 145 gÂ d.w./m2, was measured in Treskelen at low water zone.
To compare similarity between sites and points of tidal zone (LW, MW, HW), we will performe multivariate analyses based on Bray-Curtis index calculated from square root transformed data. We will estimate the biodiversity of the fauna using Shannon-Wiener (H) coefficient and the number of species.
Fig. 6. Polychaeta - infauna which bury in soft sediments
Fig. 7. Examples of other faunal representatives: mites,'Oscar' Dendronotus frondosus (ascanius) at Wilczekodden intertidal pool and ostracod.
We would like to thank dr Marek ZajÄ
czkowski who provided facilities for the field trip to Hornsund in 2003 and his help during fieldwork. Also we wish to thank prof. Jan Marcin WÄsĹawski for his comments, advices and kind assistance during lab work.
We are grateful to all members of Institute of Ecology, Polish Academy of Sciences for their friendliness and help.
We wish to express our appreciation for the hospitality of the crew of Polish Polar Station in Hornsund.