Pisternick, Timo, Neehaul, Yashvin, Dumur, Danishta, Döring, Julian, Ekau, Werner and Moosdorf, Nils (2018) Increased abundance and biodiversity of reef fishes in a lagoonal system affected by submarine groundwater discharge. [Talk] In: Youmares 9. , 11.-14.09.2018, Oldenburg .

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Submarine inflow of freshwater from land into the ocean (fresh submarine groundwater discharge, FSGD) is increasingly recognized as an important source of local nutrient and pollutant influx to coastal ecosystems. Still, very little is known about the effects of FSGD on ecosystem functioning. While there is evidence of a positive link between FSGD derived nutrients and phytoplankton abundances, further research is needed to assess the effects of FSGD on the productivity of higher trophic levels such as ichthyofaunal communities.
To follow up on this relationship, we sampled two sites in a tropical coastal lagoon (Trou aux Biches, Mauritius) during early summer months (October – December 2017). The hydrology in the lagoon’s southern part is highly influenced by six distinct freshwater springs, whereas the lagoon’s northern part served as a control site. At each of the two sites, abiotic parameters, nutrient concentrations, as well as the dry weight of total suspended solids (TSS), composition of benthic cover and fish abundances were recorded.
Water nutrient (PO43-, SiO44-, NO3-, NO2-, NH3) levels were significantly higher, whereas salinity and pH values were significantly lower in the SGD affected southern part when compared to the northern, strictly marine part of the lagoon. TSS and coral cover were significantly higher at the SGD site while macroalgae cover was significantly higher at the control site. In addition, the SGD site exhibited significantly higher fish species richness and diversity. Also, abundances of commercially important fish species were significantly higher in the SGD affected part of the lagoon.
Our results provide first evidence of a SGD driven positive relationship between high nutrient loadings, elevated primary production, and enhanced secondary consumer abundances in coral reef lagoons. These findings will have implications for coastal management advice and secondary consumer productivity appraisal on tropical islands.

Document Type: Conference or Workshop Item (Talk)
Research affiliation: Biogeochemistry and Geology > Submarine Groundwater Discharge
Ecology > Fisheries Biology
Affiliations > Not ZMT
Date Deposited: 01 Sep 2020 12:56
Last Modified: 01 Oct 2020 13:01
URI: http://cris.leibniz-zmt.de/id/eprint/4127

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