Population dynamics, biomass and productivity of Limapontia depressa (Gastropoda, Opisthobranchia) at Bull Island, Dublin, Ireland |
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Authors: | James G Wilson Niamh Forrest |
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Institution: | 1. Zoology Department, Trinity College, Dublin 2, Ireland ((e-mail
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Abstract: | Limapontia depressa was present in the saltmarsh pools at Bull Island, Dublin from October to June each year. Numbers peaked in December, with a secondary peak in April, and the maximum density recorded was just under 23000 indiv m–2. The strong population seasonal cycle was not linked to salinity or chlorophyll-a cycles but did coincide with the drying of the pools. Average production (P) was 233 kJ m–2 y–1, with a P:B ratio of just 2:1, which is rather low for such a small animal and may be a function of the low growth rate. These conclusions must be treated with caution due to uncertainty over recruitment mechanisms. Gamete output (G) was calculated at a maximum of 28.6 kJ m–2 y–1. This is a higher secondary production than previously reported for saltmarsh herbivores, and may be an important link into the wider estuarine trophic system and a vital food resource for small waders. The low G:P ratio suggests that not all semelparous species necessarily adopt an r-strategy of 'reproductive recklessness'. |
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