Spatio-temporal variation in harpacticoid copepod assemblages and of their food sources in an estuarine intertidal zone
Cnudde, C.; Stock, W.; Willems, A.; Rigaux, A.; De Troch, M.; Moens, T. (2013). Spatio-temporal variation in harpacticoid copepod assemblages and of their food sources in an estuarine intertidal zone, in: Cnudde, C. Trophic ecology of intertidal harpacticoid copepods, with emphasis on their interactions with bacteria = Trofische ecologie van intertidale harpacticoide copepoden, met de nadruk op hun interacties met bacteriën. pp. 25-50 In: Cnudde, C. (2013). Trophic ecology of intertidal harpacticoid copepods, with emphasis on their interactions with bacteria = Trofische ecologie van intertidale harpacticoide copepoden, met de nadruk op hun interacties met bacteriën. PhD Thesis. Ghent University (UGent): Gent. ISBN 9789090278285. 209 pp., more |  |
| Authors | | Top | | - Rigaux, A.
- De Troch, M., more
- Moens, T., more
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| Abstract | Spatio-temporal patterns in harpacticoid assemblage composition and in individual abundances of harpacticoid species were studied in an estuarine intertidal area with high habitat heterogeneity and in relation to spatio-temporal patterns in environmental variables including sediment abiotic characteristics (granulometry, nutrient concentrations), organic matter availability, organic matter quality (chlorophyll a and pheophytine, protein content, lipid content), composition of microphytobenthos biofilms (carotenoid pigments) and sediment bacterial abundances. The tidal flat (a sand flat and a mud flat) and the salt marsh region (a Spartina-dominated sandy sediment, a Spartina-dominated muddy sediment and a muddy gully) were sampled over 4 sampling events. The two tidal flat stations have distinct harpacticoid assemblages while the harpacticoid assemblages of salt marsh stations were composed of the same abundant harpacticoid families. The influence of abiotic habitat characteristics (e.g. granulometry, inorganic nutrients) and biotic characteristics relating to food source availability and quality (total organic matter, microphytobenthic biofilms characterised by pigments and their degradation products, differences in detrital origin) on harpacticoid assemblage structure was determined and species-specific responses to environmental factors were revealed. Spatial harpacticoid assemblage variation was assigned to five variables: ammonium concentrations, total organic matter, abundance and composition of microbial biofilms (chlorophyll a proportion of total organic matter; proportion of diatoxanthin in the microphytobenthos) and abundance of detritus (pheophytine over chlorophyll a). However, harpacticoid assemblages of tidal flats were seemingly structured by abiotic factors (granulometry and tidal height) and especially copepod species from the sand flat (Paraleptastacus spinicauda, Asellopsis intermedia) were highly specific in space and constant over time. High intercorrelations between variables and especially granulometry presumably masked the role of granulometry. In contrast, the high resemblance among salt marsh harpacticoid assemblages is in spite of differences in salt marsh granulometry, and points towards a primary influence of food availability and food quality. Variability in Microarthridion littorale abundances related to microphytobenthos abundance. For Ectinosomatidae and Tachidius discipes, the low densities and low correlations over all environmental factors points towards a low affinity with the sediment surface and a generalistic occurrence, respectively. For some species, linkages between habitat characteristics and species distributions were little decisive (e.g. Platychelipus littoralis, Paronychocamptus nanus, Amphiascus sp. 1). Overall, it is not possible to denote with certainty the main variables regulating harpacticoid species distributions due to complex intercorrelations between environmental variables, including abiotic and food-related variables. |
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