What can we learn about changes in coastal food web structure after the round goby invasion?

The round goby (Neogobius melanostomus) is extremely invasive fish species, capable to reach high abundance and make significant impact on invaded ecosystem. First round gobies occured in the Lithuanian part of the Baltic Sea in 2002. The population passed establishment (2002-2010), expansion (2011-2012) and adjustment (2013-2015) phases. Rapid round goby abundance increment induced dramatic decline of its major prey - the blue mussel (Mytilus edulis), which in turn negatively affected population of wintering long-tailed duck (Clangula hyemalis). Food competition between round goby and long-tailed duck was evaluated analysing changes in their diet composition, feeding efficiency and feeding niche overlap during different round goby invasion phases. During establishment both species preyed mainly on M. edulis; during expansion, the diet of round goby was dominated by M. edulis, Crangon crangon and Macoma balthica, while in the last invasion period it shifted to polychaetes. Long-tailed duck shifted its diet from epibenthic blue mussel to fish prey during round goby expansion and adjustment phases. Feeding efficiency of the round goby decreased from 100% (percentage of full guts) determined during establishment to 80% and 68% during expansion and adjustment phases, respectively. The highest percentage of feeding long-tailed ducks was observed in the beginning of round goby invasion (74%), it dramatically declined during 2011-2012 (26%) and recovered (53%) during 2015-2016. Feeding niche overlap between round goby and long-tailed duck was biologically significant during round goby establishment, but it lost significance after drastic decline of the blue mussel in natural environment

Can an oligotrophic coastal lagoon support high biological productivity? Sources and pathways of primary production

Coastal lagoons are among the most productive systems in the world. Many marine species make use of this by entering the lagoons as juveniles for nursery and growth before returning to the sea for reproduction. Humans take advantage of such fish migration processes by fishing, and exploit the high productivity for aquaculture activities. The Mar Menor is one of the largest coastal lagoons in the Mediterranean, sustaining relatively high fishing intensity despite the fact that it has traditionally been characterized as highly oligotrophic. However, in the last decades, this lagoon has suffered drastic changes induced by human activities. This has led to eutrophication, which started mainly as a consequence of changes in agricultural practices in the lagoon watershed, and triggered such fundamental changes in the system, as the mass development of jellyfish. The aim of this work is to capture and analyse the structure and functioning of the trophic web of the Mar Menor when it was still, in contrast to other coastal lagoons, oligotrophic, to provide a start point for analysing the consequences of changes in the distribution of macrophyte meadows and of eutrophication. We have compiled a detailed trophic model of this lagoon, comprising 94 compartments, using an ECOPATH model to capture the period 1980–1995. At this time the lagoon was an autotrophic system with a high net surplus of production that reached 9124.31gC/m2/year, while the production/biomass (P/B) ratio reached 34.56 and the total primary production/total respiration ratio was 7.01. The lagoon exported a 38.46% of total flows, including the catch by fishing, and 44.40% went to detritus. The primary production was mainly benthic (99.4%) due to the microphytobenthos and macrophytes. However, despite the fact that total fishery landings in the study period ranged between 144,835.5 and 346,708.5 kg, the gross efficiency was low, making up only 0.005% of the net primary production. This could partly be explained by the high trophic level of the fish catch (2.9), but mainly because most of the primary production (10,532.06 gC/m2/year) went directly to the detritus pool and was accumulated in the sediment in the Caulerpa prolifera meadows. We suggest several reasons why such high productivity coincided with low chlorophyll concentrations and good overall water quality: 1) the domination of both benthic biomass and primary production over pelagic ones with a high biomass of filter feeders, detritus feeders and scavengers, 2) high species diversity, complex and long food webs characterized by low connectance,3) the export of a significant part of the production from the system, and 4) the accumulation of surplus organic matter (as detritus) in sediments. We compare the food web of the Mar Menor in this mentioned oligotrophic stage to those of ten other lagoons in pursuit of more general implications regarding lagoon ecosystem functioning

A bottom-up practitioner-derived set of Essential Variables for Protected Area management

Assessing the environmental status of Protected Areas (PAs) is a challenging issue. To indicate that status, the identification of a common set of variables that are scientifically sound, and easy to assess and monitor by the PA practitioners, is particularly important. In this study, a set of 27 Essential Variables (EVs) for PA management was selected in a bottom-up process from 67 harmonised variables that describe the status of Ecosystem Functions and Structures, Ecosystem Services, and Threats in PAs. This bottom-up process involved 27 internationally recognised PAs, mostly European, with different level of protection, different extent, and a wide range of human-nature interactions. The EVs were selected by more than 120 practitioners, i.e. PA managers and rangers, as well as scientists, working in terrestrial and aquatic PAs. Across both terrestrial and aquatic PAs, scientists and practitioners largely identified the same variables as important. Data availability for these 27 EVs varied between PAs and averaged 67% across all studied PAs. As this set of EVs for PAs is defined through a bottom-up approach considering variables already in use both in management and research, it is more than for previous EVs likely to be adopted, applied and developed to record the status and changes in the ecological and socio-economic conditions of PAs and to forecast future changes. Thereby, the EVs for PAs present a common vocabulary and tool to enhance in a uniform way the (inter)national communication, exchange and comparison of information on the status of PAs between policy makers, scientists and PA managers. The perceived status of the EVs, on an average 3.6 on a scale to a maximum of 5, indicates the surveyed PAs are in a moderate to good environmental condition. Moreover, the EVs for PAs form a cost- and time-efficient tool for PA managers to monitor developments in essential elements of their PAs, including the potential for Societal Goods and Benefits (SG&B), and to (pro-)actively tackle the potential threats that may arise in their area. Likewise, for policy makers EVs for PAs may support decision making on ecosystem management, spatial planning, and predictive modelling on the future status and requirements of PAs in their country or region.