Abstract
Submarine groundwater discharge (SGD), the direct discharge of groundwater into the sea, is widely spread. Fresh SGD can occur as focused flow in submarine springs. However, little is known on the impact of submarine springs on marine organisms. For a better understanding of the interaction between SGD and its surrounding organisms, the impact of SGD on the abundance of fish was investigated in a coastal lagoon of Tahiti, French Polynesia. The study is based on the assumption of an enhanced biological production due to increased amounts of nutrient input caused by terrestrial groundwater supply into the sea. Biofouling processes and zooplankton samples were used as indicators for elevated nutrient input due to submarine spring. The main objective was to investigate the effect on the abundance of fish assuming a higher fish abundance possibly caused by a bottom-up control. Presented data show a significantly higher fish abundance around a submarine spring as well as significantly larger growth of algal turfs exposed to groundwater discharge. Zooplankton evaluations suggest slightly higher abundances around the submarine spring. The results suggest elevated nutrient concentrations transmitted by submarine springs may cause a bottom-up control resulting in a higher abundance of fish around the springs at the study site.
Highlights
Scientific interest in submarine groundwater discharge (SGD), the direct discharge of groundwater to the coastal waters, has strongly increased over the past years, highlighting its influence on coastal nutrient budgets (Moore, 2010; Moosdorf et al, 2015), global water budgets (Burnett et al, 2003; Kwon et al, 2014), and global biogeochemical cycles (Slomp and Van Cappellen, 2004; Cole et al, 2007; Beusen et al, 2013; Cho et al, 2018)
We present a detailed photographic study of fish at a submarine spring site located in a coastal lagoon of Tahiti, French Polynesia accompanied by observations on nutrients, primary and secondary production
The present study investigates the effect of a submarine spring on the abundance of fish in a coastal lagoon of Tahiti, French Polynesia, assuming a bottom-up control caused by elevated nutrient concentrations from a submarine spring
Summary
Scientific interest in submarine groundwater discharge (SGD), the direct discharge of groundwater to the coastal waters, has strongly increased over the past years, highlighting its influence on coastal nutrient budgets (Moore, 2010; Moosdorf et al, 2015), global water budgets (Burnett et al, 2003; Kwon et al, 2014), and global biogeochemical cycles (Slomp and Van Cappellen, 2004; Cole et al, 2007; Beusen et al, 2013; Cho et al, 2018). We present a detailed photographic study of fish at a submarine spring site located in a coastal lagoon of Tahiti, French Polynesia accompanied by observations on nutrients, primary (biofouling) and secondary production (zooplankton). Due to their location between continental and marine ecosystems, coastal lagoons are often described as boundary environments (Sarno et al, 1993). As changes in ecosystems are often based on alterations in nutrient fluxes, Johannes (1980) argued that ignoring SGD may lead to profound misinterpretation of ecological data in terms of coastal pollution, benthic zonation and productivity His data indicated that SGD locally delivers several times more nitrate to coastal waters at the assessed location than river runoff does. The present study investigates the effect of a submarine spring on the abundance of fish in a coastal lagoon of Tahiti, French Polynesia, assuming a bottom-up control caused by elevated nutrient concentrations from a submarine spring
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