Phytoplankton productivity in interlinked mangroves, seagrass and coral reefs and its ecotones in Gulf of Mannar Biosphere Reserve South east India

Abstract

The present study analysed spatio-temporal variation in phytoplankton productivity in relation to physico-chemical factors, prevailing in an interlinked system of mangroves, seagrasses and coral reefs in south India. Temperature and salinity exhibited variation between seasons but did not vary between sampling sites. Dissolved oxygen and particulate organic carbon (POC) varied between sampling sites but did not vary between seasons. pH, redox potential, reactive silicate, nitrite, total phosphate and primary productivity varied significantly between seasons as well as between sampling sites (P<0.05). In the sediment, chlorophyll a, tannin and total organic carbon (TOC) varied significantly between seasons as well as between sampling sites; total amino acids and sugars did not vary significantly between seasons or between sampling sites (P<0.05). The phytoplankton counts showed significant variation between the sampling sites as well as the seasons (P<0.05). The primary productivity was higher in the mangrove region and lower in the coral reef. The seagrass region exhibited an intermediate value. A similar trend was observed in phytoplankton counts and nutrient loads. The PRIMER analysis revealed higher diversity and species richness of phytoplankton in the mangrove region in accordance with k-dominance curve. The cluster analysis grouped mangroves and the adjacent sites in Manoli Island as a separate group. Principal component ordination, BIOENVI and Global BEST match tests revealed TOC and POC to be the most influential parameters to primary productivity. Thus the present study ascertained the importance of mangrove-derived organic matter in the primary productivity of adjacent ecosystems.

Keywords:

• Coral reefs
• mangroves
• organic carbon
• phytoplankton
• PRIMER analysis
• productivity
• seagrass

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Acknowledgements

The authors are thankful to Professor T. Balasubramanian, director of our centre and other authorities of Annamalai University for providing facilities and the Gulf of Mannar Biosphere Reserve Trust, Ramanathapuram Tamil Nadu India for providing financial support from GEF-UNDP sponsored project.

Notes

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark