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River estuaries are characterized by mixing processes between freshwater discharge and marine water masses. Since the first are depleted in heavier stable isotopes compared with the marine realm, estuaries often show a linear correlation between salinity and water stable isotopes (δ18O and δ2H values). In this study, we evaluated spatial and seasonal isotope dynamics along three estuarine lagoon transects, located at the northern German Baltic Sea coast. The data show strong seasonality of isotope values, even at locations located furthest from the river mouths. They further reveal a positive and linear salinity‐isotope correlation in spring, but ‐in two of the three studied transects‐ hyperbolic and partially reverse correlations in summers. We conclude that additional hydrological processes partially overprint the two‐phase mixing correlation during summers: aside from the isotope seasonality of the riverine inflows, the shallow inner lagoons in the studied estuaries are influenced by evaporation processes. In contrast the estuarine outflow regions are under impact of significant salinity and isotope fluctuations of the Baltic Sea. Deciphering those processes is crucial for the understanding of water isotope and salinity dynamics. This is also of relevance in context of ecological studies, for example, when interpreting oxygen and hydrogen isotope data in aquatic organisms that depend on ambient estuarine waters., Spatial and seasonal water isotope dynamics were evaluated along three estuarine lagoon transects at the German Baltic Sea coast. Data reveal a positive and linear salinity‐isotope correlation in spring, but partially reverse correlations in summers. The results show that evaporation processes in the shallow inner lagoons and varying Baltic Sea influence in the outer estuary regions are able to overprint the two‐phase mixing correlation between riverine and marine water masses., Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659, https://doi.org/10.1594/PANGAEA.937990

The EU-water framework directive (WFD) focuses on nutrient reductions to return coastal waters to the good ecological status. As of today, many coastal waters have reached a steady state of insufficient water quality due to continuous external nutrient inputs and internal loadings. This study focuses first on the current environmental status of mesohaline inner coastal waters to illustrate their needs of internal measures to reach demanded nutrient reductions and secondly, if mussel cultivation can be a suitable strategy to improve water quality. Therefore, nitrogen, phosphorus, chlorophyll a, and Secchi depth of nine mesohaline inner coastal waters in north east Germany were analyzed from 1990 to 2018. Two pilot mussel farms were used to evaluate their effectiveness as a mitigation measure and to estimate potential environmental risks, including the interactions with pathogenic vibrio bacteria. Further, estimated production and mitigation potential were used to assess economic profitability based on the sale of small sized mussels for animal feed and a compensation for nutrient mitigation. The compensation costs were derived from nutrient removal costs of a waste water treatment plant (WWTP). Results show that currently all nine water bodies do not reach the nutrient thresholds demanded by the WFD. However, coastal waters differ in nutrient pollution, indicating that some can reach the desired threshold values if internal measures are applied. The mitigation potential of mussel cultivation depends on the amount of biomass that is cultivated and harvested. However, since mussel growth is closely coupled to the salinity level, mussel cultivation in low saline environments leads to lower biomass production and inevitably to larger cultivation areas. If 50% of the case study area Greifswald Bay was covered with mussel farms the resulting nitrogen reduction would increase Secchi depth by 7.8 cm. However, high chlorophyll a values can hamper clearance rates (

Reduced precipitation treatments often are used in field experiments to explore the effects of drought on plant productivity and species composition. However, in seasonally snow-covered regions reduced precipitation also reduces snow cover, which can increase soil frost depth, decrease minimum soil temperatures and increase soil freeze-thaw cycles. Therefore, in addition to the effects of reduced precipitation on plants via drought, freezing damage to overwintering plant tissues at or below the soil surface could further affect plant productivity and relative species abundances during the growing season. We examined the effects of both reduced rainfall (via rain-out shelters) and reduced snow cover (via snow removal) at 13 sites globally (primarily grasslands) within the framework of the International Drought Experiment, a coordinated distributed experiment. Plant cover was estimated at the species level and aboveground biomass was quantified at the functional group level. Among sites, we observed a negative correlation between the snow removal effect on minimum soil temperature and plant biomass production the next growing season. Three sites exhibited significant rain-out shelter effects on plant productivity, but there was no correlation among sites between the rain-out shelter effect on minimum soil moisture and plant biomass. There was no interaction between snow removal and rain-out shelters for plant biomass, although these two factors only exhibited significant effects simultaneously for a single site. Overall, our results reveal that reduced snowfall, when it decreases minimum soil temperatures, can be an important component of the total effect of reduced precipitation on plant productivity.

Current classification systems of marine habitats in the Mediterranean are based on homogeneous categories. However, the natural benthos is not homogeneous and there is a need to explicitly recognize and quantify the extent of habitat edges, the unique conditions and resources they offer, and the unique animal communities they support. We predicted that species seek edge habitats due to their predation mode or their ability to exploit more varied resources. We found a significant heterogeneity effect: edge habitats have higher fish abundance, species richness, and diversity than homogenous habitats. Species more abundant at edges have diets with significantly higher taxon diversity. Edge seeking species result in unique fish ssemblages. Management of fish biodiversity should recognize the conservation value of edge habitats.

In this publication, we will report on new records for two fi sh species Sparisoma cretense and Xyrichtys novacula in the Southern Adriatic Sea (Croatia), found in August 2011. Both species are potential indicators for tropicalization. All specimens were visually detected and identifi ed over the course of a long term fi sh survey (dating back to 2009) involving a lure assisted visual census. S. cretense has been observed at locations in the Molunat and Cavtat areas while the X. novacula specimens have been observed at a SE location at Korcula Island. The 2009-2011 survey has so far covered a total of 100 sites representing a broad geographical range from the southernmost locations of the Croatian Adriatic (Prevlaka) to northern locations in the Gulf of Trieste and from the main coast of Croatia to islands as distant from the main shore as Lastovo Island.

Seagrass meadows are often considered the most important animal habitat of the shallow marine benthos. While Croatia has the highest linear extent of shallow benthic habitats per hectare of marine territory of any Mediterranean country, with unusually extensive beds of the seagrass Posidonia oceanica, there is yet no published study of the macrofaunal communities of Posidonia and neighboring habitats in the Croatian Adriatic. Our objective was to document the habitat value of all shallow benthic habitats in Croatia to adult and juvenile fish species. We used lure-assisted visual census in 3650 10-m belt transects at 74 locations spanning the entire Croatian coast from spring to fall 2009. More than 47000 fish of 72 species were observed at six basic habitats – rock, algae, sand, Posidonia oceanica, Cymodocea nodosa, and Zostera noltii – which also occurred in 19 distinct combinations. Highest adult fish abundance and diversity were observed on rock and algae and lowest within Cymodocea, with intermediate values within Posidonia. Mixtures of >2 habitats at the scale of meters showed a higher abundance and diversity of adult fish than

Evidence for competition between two co-occurring seagrass species, Zostera is given.