Zooplankton of the Kenya Coast: ecology and systematics

The Kenya coast is characterised by the half-year reversing Monsoon winds and by similarly alternating wet and dry seasons, which influence the marine and coastal environment and the flora and fauna therein. The geomorphology of the coastline comprising of creeks, bays and lagoons; and associated with various habitats of mangals, seagrass beds and coral influence the abundance, diversity and distribution of zooplankton (Chapter 1). Physico-chemical variations of the water are confined within narrow ranges except salinity, which is drastically reduced during the wet season. The hydrographical profile, climate and marine habitats of Kenya are presented in Chapter 2 including historical weather records of temperature, rainfall, humidity and evaporation. Research methodologies and material used are presented in Chapter 3. This study reports that zooplankton population off the Kenya coast is rich, comprising more than 300 taxa of commonly occurring holoplankton and meroplankton. The zooplankton abundance varies depending on the season and the prevailing coastal geomorphology. Gazi Bay (Chapter 4) has near pristine conditions due to its location far away from major industries. Mtwapa Creek (Chapter 7) on the contrary is exposed to constant anthropogenic influence it has however, high rates of flushing resulting to efficient water exchange with the open ocean. Mida Creek (Chapter 8) lacks rivers but has substantial groundwater discharge. During the wet season, Gazi Bay and Mtwapa Creek, which have river inlets recorded high zooplankton abundances of up to 2,000 m'3. Mida Creek recorded lower abundance of about 1,000 m‘3 during the wet season, but during the dry season it increased to about 2,800 m'3. The most abundant holoplankton, which accounted for approximately 98 % of this category were Copepoda, Medusae, Chaetognatha, Appendicularia, Foraminifera, Siphonophora, Ostracoda and Cladocera. Holoplankton taxa were consistently abundant in Gazi Bay and the Mombasa Marine Park lagoon with densities ranging from about 500 to 800 m'3. They were moderately abundant in Mtwapa Creek and Mida Creek with approximate densities of between 200 and 600 m'3. They were often less than 200 m3 in Makupa Creek (Chapters 5, 6). This creek is almost completely enclosed, has poor flushing rates and has been subjected to long term dumping of industrial and domestic wastes. Meroplankton was mainly represented by Gastropoda, Brachyura zoea, Caridea, Pisces eggs and larvae, Decapoda and Isopoda. These taxa constituted approximately 77 % of the entire meroplankton category in numbers. They were mostly abundant in Makupa Creek (Chapters 5, 6) where they often occurred in monthly densities of between 200 and 400 m'3 and occasionally more than 2,000 m'J. Copepoda, whose abundance constituted more that 70 percent of the population numerically dominated the zooplankton community. Acrocalanus, Oithona, Acartia, Pseudodiaptomus, Undinula, Corycaeus, Tortanus and Oncaea were the dominant genera and accounted for more than 90% of the total copepod population. Sixteen species of the copepod family Candaciidae were found to occur off the Kenya coast and were most abundant (up to 360 in 100 m3) in the shelf waters (Chapter 9). Candacia bradyi A. Scott, 1902; C. bipinnata Giesbrecht, 1889; C. curta (Dana, 1849), C. tuberculata Wolfenden, 1905 and C. ethiopica (Dana, 1849) were reported as new records for Kenya. New morphological characters were identified and described on specimens of Candaciidae (Chapter 10), which will be valuable in taxonomic studies

Distribution and Abundance of Candacia Dana, 1846 and Paracandacia Grice

Abstract-The distribution and abundance of copepods belonging to the genera Candacia and Paracandacia (family Candaciidae) within the inshore, shelf and offshore waters of the Kenya coast are presented. The copepod species are widely distributed, at low abundances (9 to 240 ind.100/m 3 ) within the inshore waters, which increases to a maximum (40 to 360 ind.100/m 3 ) within the shelf waters and decreases again to minimum (10 to 40 ind.100/m

Zooplankton assemblages from a tidal channel in the Bahía Blanca Estuary, Argentina

In this study we investigate for the first time the zooplankton assemblages in a relatively small tidal channel called Bahía del Medio, situated in the middle-outer area of the Bahía Blanca Estuary, South of the Main channel. We focused the study on micro- and mesozooplankton assemblages with emphasis on tintinnids, copepods and meroplankton along the annual cycle 1997-1998. Fifteen species of tintinnids belonging to 6 genera were observed in the study area, the mean total tintinnid abundance fluctuating between 3.4 x 10(6) ind. m-3 and 5.1 x 10(6) ind m-3. The mesozooplankton comprised 11 taxa, total abundance fluctuating between 449 ind m-3 in March 1997 and only 1 ind m-3 in October 1997. The channel proved to be spatially homogeneous in its physical and biochemical features. Micro- and mesozooplankton abundance displayed a high degree of spatial homogeneity, though the seasonal variation in both environment and zooplankton was significant. Comparison with the zooplankton observed at a station in the Main channel of the estuary showed differences in number of taxa represented, a general lower abundance of both assemblages and the presence of some rare species, a fact which is discussed.<br>Neste estudo pesquisamos pela primeira vez as associações do zooplâncton num pequeno canal de maré, relativamente novo e chamado Bahía del Medio, localizado na região média-exterior do estuário da Bahía Blanca e ao sul do canal principal. Focalizamos o estudo no micro- e mesozooplâncton com ênfase nos grupos Tintinnida, Copepoda e meroplâncton, ao longo do ciclo anual 1997-1998. Foram observadas 15 espécies de Tintinnida pertencentes a 6 gêneros; a abundância média total de Tintinnida variou entre 3,4 x 10(6) ind. m-3 e 5,1 x 10(6) ind. m-3. O mesozooplâncton apresentou 11 taxa e uma abundância total entre 449 ind. m-3 em março de1997 e 1 ind. m-3 em outubro de 1997. O canal provou ser espacialmente homogêneo em suas características biológicas, químicas e físicas. A abundância do micro- e mesozooplâncton mostrou um alto grau de homogeneidade espacial, embora a variaçao estacional fosse significativa nas características do meio ambiente e do zooplâncton. A comparação com o zooplâncton observado em uma estação de amostragem no canal principal do estuário mostrou diferenças no número de taxa, na abundância, em geral mais baixa, e na presença de algumas espécies raras , fato esse comentado