Christopher P. Lynam

Jellyfish overtake fish in a heavily fished ecosystem

(Current Biology 16, R492–R493; July 11, 2006)The units in the y-axis label of Figure 1A, which shows historic fish landings in the Benguela (South East Atlantic Major Area 47, Western Coastal Subarea, Divisions 1.3 Cunene, 1.4 Cape Cross, and 1.5 Orange River) from data compiled by the United Nations Food and Agriculture Organization (FAO), are mislabeled as 106 tonnes instead of 105 tonnes. The text that refers to the figure (paragraph 2, lines 11–12) is similarly in error by a factor of 10 too high; fish landings actually fell from about 1.7 million metric tonnes to 0.1 million metric tonnes. This error has no bearing on the main thrust or conclusion of our paper—that jellyfish biomass in the Benguela now exceeds that of once prolific finfish—because the recent estimates of fish and jellyfish biomass we report are from our own observations and not our interpretation of FAO data.

Jellyfish abundance and climatic variation: contrasting responses in oceanographically distinct regions of the North Sea, and possible implications for fisheries

Jellyfish medusae prey on zooplankton and may impact fish recruitment both directly (top-down control) and indirectly (through competition). Abundances of Aurelia aurita, Cyanea lamarckii and Cyanea capillata medusae (Scyphozoa) in the North Sea appear to be linked to large-scale inter-annual climatic change, as quantified by the North Atlantic Oscillation Index (NAOI), the Barents Sea-Ice Index (BSII) and changes in the latitude of the Gulf Stream North Wall (GSNW). Hydroclimatic forcing may thus be an important factor influencing the abundance of gelatinous zooplankton and may modulate the scale of any ecosystem impact of jellyfish. The population responses are probably also affected by local variability in the environment manifested in intra-annual changes in temperature, salinity, current strength/direction and prey abundance. Aurelia aurita and C. lamarckii in the north-west and south-east North Sea exhibited contrasting relationships to change in the NAOI and BSII: north of Scotland, where the North Sea borders the Atlantic, positive relationships were evident between the abundance of scyphomedusae (data from 1974 to 1986, except 1975) and the indices; whereas west of northern Denmark, a region much less affected by Atlantic inflow, negative relationships were found (data from 1973 to 1983, except 1974). Weaker negative relationships with the NAOI were also found in an intermediate region, east of Scotland, for the abundance of A. aurita and C. capillata medusae (1971 to 1982). East of Shetland, the abundance of jellyfish was not correlated directly with the NAOI but. in contrast to all other regions, the abundances of A. aurita and C. lamarckii (1971 to 1986, not 1984) were found to correlate negatively with changes in the GSNW, wliich itself was significantly positively correlated to the NAOI with a two year lag. On this evidence, we suggest that, for jellyfish, there exist three regions of the North Sea with distinct environmental processes governing species abundance: one north of Scotland, another east of Shetland, and a more southerly group (i.e. east of Scotland and west of northern Denmark). Impacts by jellyfish are likely to vary regionally, and ecosystem management may benefit from considering this spatial variability.

Global in scope and regionally rich: an IndiSeas workshop helps shape the future of marine ecosystem indicators

This report summarizes the outcomes of an IndiSeas workshop aimed at using ecosystem indicators to evaluate the status of the world’s exploited marine ecosystems in support of an ecosystem approach to fisheries, and global policy drivers such as the 2020 targets of the Convention on Biological Diversity. Key issues covered relate to the selection and integration of multi-disciplinary indicators, including climate, biodiversity and human dimension indicators, and to the development of data- and model-based methods to test the performance of ecosystem indicators in providing support for fisheries management. To enhance the robustness of our cross-system comparison, unprecedented effort was put in gathering regional experts from developed and developing countries, working together on multi-institutional survey datasets, and using the most up-to-date ecosystem models.

Effort reduction and the large fish indicator: spatial trends reveal positive impacts of recent European fleet reduction schemes

© Foundation for Environmental Conservation 2015. The online version of this article is published within an Open Access environment subject to the conditions of the Creative Commons Attribution licence http://creativecommons.org/licenses/by/3.0/ doi:10.1017/S0376892915000077 Effort reduction and the large fish indicator: spatial trends reveal positive impacts of recent European fleet reduction schemes

Bridging the Gap between Policy and Science in Assessing the Health Status of Marine Ecosystems

Human activities, both established and emerging, increasingly affect the provision of marine ecosystem services that deliver societal and economic benefits. Monitoring the status of marine ecosystems and determining how human activities change their capacity to sustain benefits for society requires an evidence-based Integrated Ecosystem Assessment approach that incorporates knowledge of ecosystem functioning and services). Although there are diverse methods to assess the status of individual ecosystem components, none assesses the health of marine ecosystems holistically, integrating information from multiple ecosystem components. Similarly, while acknowledging the availability of several methods to measure single pressures and assess their impacts, evaluation of cumulative effects of multiple pressures remains scarce. Therefore, an integrative assessment requires us to first understand the response of marine ecosystems to human activities and their pressures and then develop innovative, cost-effective monitoring tools that enable collection of data to assess the health status of large marine areas. Conceptually, combining this knowledge of effective monitoring methods with cost-benefit analyses will help identify appropriate management measures to improve environmental status economically and efficiently. The European project DEVOTES (DEVelopment Of innovative Tools for understanding marine biodiversity and assessing good Environmental Status) specifically addressed these topics in order to support policy makers and managers in implementing the European Marine Strategy Framework Directive. Here, we synthesize our main innovative findings, placing these within the context of recent wider research, and identifying gaps and the major future challenges.

Interaction between top-down and bottom-up control in marine food webs

Significance Whether environmental conditions, harvesting, or predation pressure primarily regulate an ecosystem is still a question of much debate in marine ecology. Using a wealth of historical records, we describe how climate and fishing interact in a complex marine ecosystem. Through an integrative evidence-based approach, we demonstrate that indirect effects are key to understanding the system. Planktivorous forage fish provide an important role in the system, linking bottom-up and top-down processes such that fishing can indirectly impact the plankton and environmental effects can cascade up to impact demersal fish and predatory seabirds. Cascading trophic interactions can be mediated by opposing bottom-up and top-down forces; this combination has the potential to avert regime wide shifts in community structure and functioning. Climate change and resource exploitation have been shown to modify the importance of bottom-up and top-down forces in ecosystems. However, the resulting pattern of trophic control in complex food webs is an emergent property of the system and thus unintuitive. We develop a statistical nondeterministic model, capable of modeling complex patterns of trophic control for the heavily impacted North Sea ecosystem. The model is driven solely by fishing mortality and climatic variables and based on time-series data covering >40 y for six plankton and eight fish groups along with one bird group (>20 y). Simulations show the outstanding importance of top-down exploitation pressure for the dynamics of fish populations. Whereas fishing effects on predators indirectly altered plankton abundance, bottom-up climatic processes dominate plankton dynamics. Importantly, we show planktivorous fish to have a central role in the North Sea food web initiating complex cascading effects across and between trophic levels. Our linked model integrates bottom-up and top-down effects and is able to simulate complex long-term changes in ecosystem components under a combination of stressor scenarios. Our results suggest that in marine ecosystems, pathways for bottom-up and top-down forces are not necessarily mutually exclusive and together can lead to the emergence of complex patterns of control.

Quantitative criteria for choosing targets and indicators for sustainable use of ecosystems

Graphical abstract

A Catalogue of Marine Biodiversity Indicators

A Catalogue of Marine Biodiversity Indicators was developed with the aim of providing the basis for assessing the environmental status of the marine ecosystems. Useful for the implementation of the Marine Strategy Framework Directive (MSFD), this catalogue allows the navigation of a database of indicators mostly related to biological diversity, non-indigenous species, food webs, and seafloor integrity. Over 600 indicators were compiled, which were developed and used in the framework of different initiatives (e.g. EU policies, research projects) and in national and international contexts (e.g. Regional Seas Conventions, and assessments in non-European seas). The catalogue reflects the current scientific capability to address environmental assessment needs by providing a broad coverage of the most relevant indicators for marine biodiversity and ecosystem integrity. The available indicators are reviewed according to their typology, data requirements, development status, geographical coverage, relevance to habitats or biodiversity components, and related human pressures. Through this comprehensive overview, we discuss the potential of the current set of indicators in a wide range of contexts, from large-scale to local environmental programs, and we also address shortcomings in light of current needs. Developed by the DEVOTES Project, the catalogue is freely available through the DEVOTool software application, which provides browsing and query options for the associated metadata. The tool allows extraction of ranked indicator lists best fulfilling selected criteria, enabling users to search for suitable indicators to address a particular biodiversity component, ecosystem feature, habitat or pressure in a marine area of interest. This tool is useful for EU Member States, Regional Sea Conventions, the European Commission, non-governmental organizations, managers, scientists and any person interested in marine environmental assessment. It allows users to build, complement or adjust monitoring programs and has the potential to improve comparability and foster transfer of knowledge across marine regions.

Distribution of skates and sharks in the North Sea: 112 years of change

How have North Sea skate and shark assemblages changed since the early 20th century when bottom trawling became widespread, whilst their environment became increasingly impacted by fishing, climate change, habitat degradation and other anthropogenic pressures? This article examines long-term changes in the distribution and occurrence of the elasmobranch assemblage of the southern North Sea, based on extensive historical time series (1902-2013) of fishery-independent survey data. In general, larger species (thornback ray, tope, spurdog) exhibited long-term declines, and the largest (common skate complex) became locally extirpated (as did angelshark). Smaller species increased (spotted and starry ray, lesser-spotted dogfish) as did smooth-hound, likely benefiting from greater resilience to fishing and/or climate change. This indicates a fundamental shift from historical dominance of larger, commercially valuable species to current prevalence of smaller, more productive species often of low commercial value. In recent years, however, some trends have reversed, with the (cold-water associated) starry ray now declining and thornback ray increasing. This shift may be attributed to (i) fishing, including mechanised beam trawling introduced in the 1960s-1970s, and historical target fisheries for elasmobranchs; (ii) climate change, currently favouring warm-water above cold-water species; and (iii) habitat loss, including potential degradation of coastal and outer estuarine nursery habitats. The same anthropogenic pressures, here documented to have impacted North Sea elasmobranchs over the past century, are likewise impacting shelf seas worldwide and may increase in the future; therefore, parallel changes in elasmobranch communities in other regions are to be expected.

Biodiversity in Marine Ecosystems—European Developments toward Robust Assessments

Sustainability of marine ecosystems and their services are dependent on marine biodiversity, which is threatened worldwide. Biodiversity protection is a major target of the EU Marine Strategy Framework Directive, requiring assessment of the status of biodiversity on the level of species, habitats, and ecosystems including genetic diversity and the role of biodiversity in food web functioning and structure. This paper provides a summary of the development of new indicators and refinement of existing ones in order to address some of the observed gaps in indicator availability for marine biodiversity assessments considering genetic, species, habitat, and ecosystem levels. Promising new indicators are available addressing genetic diversity of microbial and benthic communities. Novel indicators to assess biodiversity and food webs associated with habitats formed by keystone species (such as macroalgae) as well as to map benthic habitats (such as biogenic reefs) using high resolution habitat characterization were developed. We also discuss the advances made on indicators for detecting impacts of non-native invasive species and assessing the structure and functioning of marine food-webs. The latter are based on indicators showing the effects of fishing on trophic level and size distribution of fish and elasmobranch communities well as phytoplankton and zooplankton community structure as food web indicators. New and refined indicators are ranked based on quality criteria). Their applicability for various EU and global biodiversity assessments and the need for further development of new indicators and refinement of the existing ones is discussed.