Species Composition of Benthic Diatoms and Distribution of Chlorophyll a on an lntertidal Flat in the Dutch Wadden Sea

Abstract

A linear transect with 12 sampling points was sampled in a tidal estuarine environment during 1973 for chlorophyll a and pheophytin, and for species composition of epipelic diatoms. A gradual pattern in sediment from coarse to fine was found from the most seaward station towards the most landward station of the transect. Differences in station level gave emersion times of 37 to 67 % of the tidal cycle. In the course of the year, fluctuations in chlorophyll a content (mg chlorophyll a m-* in the top 2 cm of the sediment) appeared to be distinctly parallel at all stations. However, mean yearly values differed widely from station to station, ranging between 20 and 100mg chlorophyll a m-2. Chlorophyll a concentration was positively related to the amount of particles < 16 pm in the sediment; this proportion was considered to relate negatively to the degree of exposure to currents and wave action. It is likely that low daily winter irradiances limited diatom growth. Heavy rain and strong wave action during storms suddenly reduced the chlorophyll a content considerably. Species composition of epipelic benthic diatoms could partly b e related to the sediment gradient and time of year. It seems that high biomass values are formed almost exclusively by single species which are indifferent in their spatial distribution.

The microphytobenthos of Königshafen—spatial and seasonal distribution on a sandy tidal flat

“…The whole species list shows a great similarity with those found by Cohjn & Koeman, (1975), Colijn & Nienhuis (1978) and Colijn & Dijkema (1981), all of whom worked further south in the Wadden Sea; therefore, this accordance could be expected. The species composition is also comparable to that of other estuaries in Europe and North America.…”

“…In the Elbe estuary, a spring bloom occurred in May (GMje, 1992). In the Ems-Dollard estuary, the bloom started in March, reaching its maximum in May-June (Colijn & Dijkema, 1981). Here, the abundance of benthic diatoms was minimal in summer, as was also found in a rocky area in Australia (Underwood, 1984).…”

“…Salinity becomes important to diatoms in estuaries (Van der Werff, 1960;McIntire & Overton, 1971;Amspoker & McIntire, 1986). Also water currents, waves, turbulence and other weather conditions can have a strong impact on the benthic diatom assemblages (Amspoker, 1977;Colijn & Dijkema, 1981;Korte & Blinn, 1983;de Jonge, 1992). Out of the multitude of chemical compounds in sediments, inorganic nutrients promote microphytobenthos (Sundb~ck & Snoeijs, 1991).…”

The importance of grazing food chain for energy flow and production in three intertidal sand bottom communities of the northern Wadden Sea

“…The area of investigation is especially suitable because of little domestic, and no direct industrial sewage influence, also by the occurrence of the typical dominant intertidal benthic communities of the Wadden Sea within a small, well defined area. The species composition of the microflora communities is similar to that found in other areas of the Wadden Sea (Brockmann, 1950;Colijn & Koeman, 1975;Colijn & Dijkema, 1981). The structure of the macrofauna (Linke, 1939;Beukema, 1976).…”

Microphytobenthic dynamics in a Wadden Sea intertidal flat – Part II: Seasonal and spatial variability of non-diatom community components in relation to abiotic parameters

“…Wind and, especially, tidal currents are usually the most important causes of mixing in intertidal flats and help to determine the distribution and abundance of several species of macrofauna Correspondence to: Bettina Scholz. E-mail: bettina.scholz@uni-oldenburg.de and the MPB (Colijn & Dijkema, 1981;Delgado et al, 1991;de Jonge & van Beusekom, 1995). Other factors influencing the spatial distribution of different organisms are light intensity and grain size composition, directly affecting many species by limiting vertical distribution and burrowing performance (Asmus, 1982).…”