Fish larvae abundance is related to zooplankton composition and physicochemical properties in mangrove-seagrass seascapeass seascapes of Zanzibar (Tanzania)

Fish larvae abundance is related to zooplankton composition and physicochemical properties in mangrove-seagrass seascapes of Zanzibar (Tanzania)
Barnabas Tarimo1, 2, Monika Winder1, Peter Thor3, Martin Gullström4*
1Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden 
2Institute of Marine Sciences, University of Dar es Salaam, Zanzibar, Tanzania
3Swedish University of Agricultural Sciences, Department of Aquatic Resources, Lysekil, Sweden
4School of Natural Sciences, Technology and Environmental Studies, Södertörn University, Huddinge, Sweden
*Corresponding Author E-mail: tarimobarnabas@yahoo.com
Abstract
Mangroves and seagrass meadows constitute essential habitats of the coastal seascape, particularly through their multifunctional role, including being important nursery grounds for many fish species. Nevertheless, there is scarcity of information about food-web dynamics and interaction and water physicochemical properties in association with fish larvae abundance and diversity in these seascapes. We investigated the influence of water physicochemical properties and abundances of zooplankton on fish larvae abundance and diversity. Fish larvae, water physicochemical variables (chlorophyll a concentration, temperature, salinity) and zooplankton were sampled monthly in three habitats: mangroves creeks, inshore and nearshore seagrass. These data were then used to model the influence of variations in water physicochemical parameters and different zooplankton taxa on fish larvae abundance and diversity using partial least squares (PLS) regression analysis. Our study found that salinity correlated negatively with fish larvae abundance and maintain the association throughout the seasons, sites and habitats, whereas water temperature showed a positive correlation with fish larvae abundance across space and time. In Chwaka Bay, seascape fish larval abundance exhibited a positive association with the abundance of selected zooplankton taxa, including copepods, gastropod larvae, bivalve larvae, and cirripedia larvae across the seasons. In Fumba, non-copepod zooplankton, namely bivalve, cirripedia, and gastropod larvae, and calanoid copepod abundances were negatively connected with the abundance of fish larvae throughout the habitats over the seasons. Our findings highlight the influence of salinity, temperature and chlorophyll a and zooplankton abundance on fish larvae abundance in mangrove-seagrass areas. The associations of salinity, temperature and chlorophyll a and zooplankton with fish larvae abundance and variations across the seascape differences are discussed.

Keywords: Fish larvae, seagrass, mangroves, zooplankton, chlorophyll a concentration, temperature, salinity