Seasonal dynamics of meiofauna in a South African temporarily open/closed estuary (Mdloti Estuary, Indian Ocean)

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• 作者：Nozais ; Christian ; Perissinotto ; Renzo ; Tita ; Guglielmo
• 关键词：meiofauna ; microphytobenthos ; biomass ; grazing ; temporarily open/closed estuary ; South Africa
• 刊名：Estuarine, Coastal and Shelf Science
• 出版年：2005
• 出版时间：January, 2005
• 年：2005
• 卷：62
• 期：1-2
• 页码：325-338
• 全文大小：764 K

文摘

One hundred and eighty-four of the 250 estuaries in South Africa are currently classified as temporarily open/closed and close off from the sea during the dry season, under low river inflow. The subtropical Mdloti Estuary, on the KwaZulu-Natal north coast, is one of these systems and hardly any information is available on its meiofauna. The abundance, biomass, composition, and grazing impact of meiofauna, as well as the key environmental factors that affect these variables, were investigated with emphasis on the contrast between open and closed phases of the estuary. Microphytobenthic chlorophyll a concentrations varied between 1.4 to 480 mg m⁻². Meiofauna were composed of nematodes, harpacticoid copepods, crustacean nauplii, mites, turbellarians, polychaetes, oligochaetes, ostracods and chironomids. Total abundance of meiofauna showed large variability both spatially and temporally and ranged from 0.4 to 88×10⁴ ind. m⁻². Nematodes, mites and harpacticoid copepods occurred more often than other groups in the sediment. Total meiofauna carbon biomass exhibited similar temporal as well as spatial patterns as abundance and varied from 0.5 to 440 mg C m⁻². A carbon-based grazing model, applied to the total meiofauna, provided estimates of potential daily ingestion rates ranging from 1.8 to 857 mg C m⁻². Nematodes, mites and harpacticoid copepods contributed the most to the total potential daily ingestion rate of meiofauna in the Mdloti Estuary. Potential ingestion rates, determined using allometric equations, showed that meiofauna consumed from 0.1 to 254 % of the microphytobenthic standing stock. Overall, meiofauna were likely not food limited and grazing on microphytobenthos was low, averaging 11 % for the whole survey. A principal component analysis, applied to the whole study area and sampling period, indicated that major variations in meiofaunal community are mainly controlled by temperature and the state of the estuary's mouth (i.e. open/closed). Typically, meiofauna abundance in the estuary peaked after periods of prolonged mouth closure and decreased dramatically after the breaching of the estuary at the mouth.