Using Stable Carbon and Nitrogen Isotopes to Investigate the Impact of Desalination Brine Discharge on Marine Food Webs

Stable isotope ratios were used to trace the impact of anthropogenically derived brine from desalination plants on organisms at different trophic levels (primary producers and consumers) along the highly urbanized ultra-oligotrophic Israeli coast (southeast Mediterranean). Primary producer and consumer organisms were collected from two sampling stations at two desalination plants sites: an “Impacted station,” near the brine discharge outlets, and a “Control station” situated further offshore to the impacted zone. δ13C and δ15N values of both producers and consumers displayed minor variations between the impacted and control stations, indicating little effect of brine discharge on the coastal trophic structure. The coastal δ15N values were generally higher than those of similar pelagic communities of the southeastern Mediterranean. These were particularly high in benthic invertebrates and benthic carnivores (fish) from the southern site, where high anthropogenically N loads from ground water amelioration are discarded alongside the brine. The observed differences in the δ15N of the benthic components between the two study sites suggest that brine derived density plumes from desalination plants are a possible vector of nutrients to benthic communities. The results indicate that the benthic components were the most sensitive group to anthropogenic derived N pollution, and provide insight into site-specific processes

Ocean warming is the key filter for successful colonization of the migrant octocoral Melithaea erythraea (Ehrenberg, 1834) in the Eastern Mediterranean Sea

Climate, which sets broad limits for migrating species, is considered a key filter to species migration between contrasting marine environments. The Southeast Mediterranean Sea (SEMS) is one of the regions where ocean temperatures are rising the fastest under recent climate change. Also, it is the most vulnerable marine region to species introductions. Here, we explore the factors which enabled the colonization of the endemic Red Sea octocoral Melithaea erythraea (Ehrenberg, 1834) along the SEMS coast, using sclerite oxygen and carbon stable isotope composition (delta O-18(SC) and delta C-13(SC)), morphology, and crystallography. The unique conditions presented by the SEMS include a greater temperature range (similar to 15 degrees C) and ultra-oligotrophy, and these are reflected by the lower delta C-13(SC) values. This is indicative of a larger metabolic carbon intake during calcification, as well as an increase in crystal size, a decrease of octocoral wart density and thickness of the migrating octocoral sclerites compared to the Red Sea samples. This suggests increased stress conditions, affecting sclerite deposition of the SEMS migrating octocoral. The delta(OSC)-O-18 range of the migrating M. erythraea indicates a preference for warm water sclerite deposition, similar to the native depositional temperature range of 21-28 degrees C. These findings are associated with the observed increase of minimum temperatures in winter for this region, at a rate of 0.35 +/- 0.27 degrees C decade(-1) over the last 30 years, and thus the region is becoming more hospitable to the IndoPacific M. erythraea. This study shows a clear case study of "tropicalization" of the Mediterranean Sea due to recent warming

Trophic position of Otodus megalodon and great white sharks through time revealed by zinc isotopes

Diet is a crucial trait of an animal’s lifestyle and ecology. The trophic level of an organism indicates its functional position within an ecosystem and holds significance for its ecology and evolution. Here, we demonstrate the use of zinc isotopes (δ66Zn) to geochemically assess the trophic level in diverse extant and extinct sharks, including the Neogene megatooth shark (Otodus megalodon) and the great white shark (Carcharodon carcharias). We reveal that dietary δ66Zn signatures are preserved in fossil shark tooth enameloid over deep geologic time and are robust recorders of each species’ trophic level. We observe significant δ66Zn differences among the Otodus and Carcharodon populations implying dietary shifts throughout the Neogene in both genera. Notably, Early Pliocene sympatric C. carcharias and O. megalodon appear to have occupied a similar mean trophic level, a finding that may hold clues to the extinction of the gigantic Neogene megatooth shark.publishedVersio

Bulk stable isotopes of deep sea fish and crustaceans from the Southeastern Mediterranean Sea

Sampling campaigns were conducted onboard of R/V Bat-Galim in the course of three oceanographic cruises conducted during 2017-2019, as part of the national deep-water monitoring program of the Israeli Mediterranean Sea performed by Israel Oceanographic and Limnological Research (IOLR). Deep sea fish and crustaceans were collected by a semi-balloon trawl net in the following transects (32.588583°N 34.763598°E to 32.526467°N 34.7362113°E; 32.627207°N 34.737953°E to 32.579127°N 34.699993°E; 32.6978475°N 34.53706267°E to 32.635671°N 34.5038796°E; 32.7248886°N 34.3501125°E to 32.77411°N 34.380888°E). Sampling sites were divided into three major benthic habitats: (1) the end of the continental shelf, with an average depth of 200 m; (2) the continental slope with a depth range of 500-600 m; and (3) the deep bathyal plateau (continental rise) with a depth range of 1000-1400 m. Fourteen species of bathypelagic fishes and six species of bathybenthic decapod crustaceans were collected, weighed and their total length was measured. Bulk δ13C and δ15N isotope data of the fish and crustaceans were analyzed. Raw data include individual weight and length, δ13C, δ15N, and C/N ratio

Experiment on biogeochemical changes following Rhopilema nomadica decomposition

This study estimated the short-term decomposition effects of the invasive jellyfish Rhopilema nomadica on nutrient dynamics at the sediment-water interface in the Eastern Mediterranean Sea using core incubations. The degradation of R. nomadica has led to increased oxygen demand and acidification of overlying water as well as high rates of dissolved organic nitrogen and phosphate production

Tooth oxygen isotopes reveal Late Bronze Age origin of Mediterranean fish aquaculture and trade

Abstract Past fish provenance, exploitation and trade patterns were studied by analyzing phosphate oxygen isotope compositions (δ18OPO4) of gilthead seabream (Sparus aurata) tooth enameloid from archaeological sites across the southern Levant, spanning the entire Holocene. We report the earliest evidence for extensive fish exploitation from the hypersaline Bardawil lagoon on Egypt’s northern Sinai coast, as indicated by distinctively high δ18OPO4 values, which became abundant in the southern Levant, both along the coast and further inland, at least from the Late Bronze Age (3,550–3,200 BP). A period of global, postglacial sea-level stabilization triggered the formation of the Bardawil lagoon, which was intensively exploited and supported a widespread fish trade. This represents the earliest roots of marine proto-aquaculture in Late Holocene coastal domains of the Mediterranean. We demonstrate the potential of large-scale δ18OPO4 analysis of fish teeth to reveal cultural phenomena in antiquity, providing unprecedented insights into past trade patterns

P fluxes and prokaryotic cycling at benthic boundary layer in the deep southeastern Mediterranean Sea

The sediment-water interface is a site of active nutrients exchange between the geosphere and the hydrosphere. We quantified fluxes of dissolved inorganic and organic phosphorous between the deep sediments and the overlying waters of the P-limited southeastern Mediterranean Sea (SEMS) using sediment core incubations. Sediments were collected throughout the Israeli exclusive economic zone and analyzed for their pore-water physicochemical characteristics. We also designed custom-made incubation flux chambers and followed dissolved inorganic and organic phosphorous dynamics as well as prokaryotic microbial activity in the overlying waters for several days. We show that due to the low organic matter content and the well-oxygenated conditions, the sediments of the SEMS function as a PO4 sink. The sedimentary net removal flux of P is equal to a turnover time of ~90 years, similar to the deep water residence time in this basin, hence contributing to the low concentration of PO4 in the deep water of the SEMS. Our incubation experiments show that aside from abiotic processes, such as, adsorption and co-precipitation of PO4, prokaryotic microbial activity play a pivotal role in P-recycling, resulting in a flux of dissolved organic P (DOP) to the overlaying. Organic molecules containing P and C are a known limiting factor for bacteria, and upon release from the sediment stimulated increased prokaryotic microbial activity. Our results highlight the role of the seabed as a hot-spot for microbial activity