ALBERT

Description: Submarine groundwater discharge (SGD) in to the sea is widely spread and investigated. However, on the impact of SGD on marine organisms in turn very view work has been done. For a better understanding of the interaction between SGD and its surrounding organisms, the impact of SGD on fish and zooplankton abundances as well as on the early biofouling process was investigated in a coastal la goon of Tahiti, French Polynesia. This study is based on the hypothesis of an enhanced biological production due to increased amounts of nutrient input caused by terrestrial fresh water supply to the sea. Presented data showed a significantly larger growth of algal turfs exposed to the freshwater spring. Plankton evaluations suggest ed slightly higher wet weights and abundances around the freshwater. The implemented stationary photo sampling of fish resulted likewise in a significantly higher fish occurrence around the freshwater spring. The presented data suggest that the elevated nutrient concentrations transmitted by SGD may cause a bottom up control resulting in higher zooplankton and fish abundances around SGD.

Description: Little is known about the concerted influence of temperature and salinity on the fecundity of clupeid fishes. Due to a globally changing climate, both physical parameters might act as stressors, severely affecting the reproductive potential of clupeid fish populations inhabiting tropical estuaries. Differences in relative batch fecundities, the gonado-somatic index, and the condition index of bonga shad (Ethmalosa fimbriata) were analysed in individual females sampled at the Senegalese coast and inside the inverse Sine Saloum estuary, where salinity increases upstream in all seasons. Sampling took place at the Senegalese coast and inside the Saloum River from February to October 2014, during the peak of E. fimbriata's spawning season. An additional sampling campaign could be conducted in November 2016. Three different sites were sampled: Joal (Senegalese coast, 14°9.1' N; 16°51.7' W), Djifer (Saloum River's mouth, 13°57.8' N; 16°44.8' W), and Foundiougne (upstream Saloum River, 14°8.1' N; 16°28.1' W). MODIS satellite-derived (Aqua, level 2, 0.1 degrees) sea surface temperatures (https://oceancolor.gsfc.nasa.gov/) were assessed at Joal (20 km radius) and Djifer once per sampling week to enhance spatial coverage by avoiding cloud cover. As no remote sensing data for inland waters were available, the Saloum River's surface water temperatures were recorded in situ once per sampling week with a digital thermometer (ama-digit ad 15 th; precision 0.4%; accuracy 0.4%). Monthly means in MODIS satellite-derived (Aquarius, level 3, 0.5 degrees) sea surface salinities (https://oceancolor.gsfc.nasa.gov/) were used to assess the coastal ocean's salinity in a radius of 20 km around Joal. For Djifer and Foundiougne salinity was measured with a handheld refractometer (Aqua Medic; precision 0.7%, accuracy 0.2%) using a Practical Salinity Scale (PSS-78). Staging of fish was conducted macroscopically after a key by Blay Jr. & Eyeson (1982). In order to discriminate between mature females with ovaries containing fully hydrated oocytes (stage V) and females that have recently spawned (spent, stage VI) further descriptions on maturity stages in clupeid fishes were consulted (West 1990, ter Hofstede et al. 2007). Conversions of fish fork length (LF) to total length (LT) were conducted using the equation LT = 1.0007 × LF + 3.9. In order to access the nutritional status of female fish, a condition index (CI) was calculated for each individual using wet mass (WM, ±0.1 g), total length (LT, nearest mm), and b of the length-weight relationship: CI = WM x LT ^ -3.62 x 1000. The condition index (CI) and gonado-somatic index (GSI) of hydrated female spawners (Stage V) was based on the ovary-free body mss (OFBM, ±0.1 g) and the ovary mass (OM, ±0.0001 g): CI = WOF x LT ^ -3.62 x 1000; GSI = OM x OFBM ^ -1 x 100. The length-weight relationship of all sampled females across all sampling sites could be described by the following function: WM = 0.0015 x LT ^ 3.62

Description: Inversion of estuaries in the dry tropics (i.e. salinity increases upstream) in front of the backdrop of a globally changing climate forces migratory clupeid fish species to adapt quickly to modifications in their spawning habitats in order to ensure reproductive success. Hatching success and survival probabilities of marine fish eggs and early life stages are prone to impairment under high temperature and elevated salinity conditions. Essential fatty acids affect osmoregulation in marine fish early life stages and deficiencies can therefore be expected to cause elevated offspring mortality under hyperosmotic conditions, ultimately modifying a stock's reproductive potential. Monthly sampling of Ethmalosa fimbriata females storing hydrated oocytes was conducted at the Senegalese coast and inside the Sine Saloum estuary from February to October 2014, during Ethmalosa fimbriata's main spawning period. Three different sites were sampled; Joal (coast, 14°9.1' N; 16°51.7' W), Djifer (River mouth, 13°57.8' N; 16°44.8' W), and Foundiougne (upstream Saloum River, 14°8.1' N; 16°28.1' W). A supplementary sampling campaign was conducted in November 2016. Here, microphytoplankton was collected by casting a handheld net (20 µm mesh size) three times per station. Additionally, the stomach content of 10 female fishes per sampling site, and the counted oocytes of 12 females were sampled. During this sampling trip, phytoplankton could also be sampled at Ndjiafate (upstream Saloum River, 14°3.7' N; 16°11.4' W). The coastal waters off Joal and in the Saloum River are well-mixed and do not show significant stratification. Thus, only surface water temperatures and salinities were measured for each sampling week. Water temperatures at Foundiougne and Ndiafate were recorded with a digital thermometer (ama-digit ad 15th; precision 0.4%; accuracy 0.4%). For Joal, where catch positions could only be estimated within a radius of ~20 km, and Djifer, average night-time sea surface temperatures were assessed by means of MODIS satellite-data (Aqua, level 2, 0.1 degrees)(https://oceancolor.gsfc.nasa.gov/). For Joal, monthly means in MODIS satellite-derived (Aquarius, level 3, 0.5 degrees) sea surface salinities (https://oceancolor.gsfc.nasa.gov/) were used. At Djifer, Foundiougne, and Ndjiafate salinity was determined with a handheld refractometer (Aqua Medic; precision 0.7%, accuracy 0.2%) using in situ water samples. Fatty acid methyl esters were analysed using GC-FID. To ensure comparability with past studies, results for fatty acids (FA) are given as a percentage of the combined weights of all detected FA.