Guillem Chust

Biomass changes and trophic amplification of plankton in a warmer ocean

Ocean warming can modify the ecophysiology and distribution of marine organisms, and relationships between species, with nonlinear interactions between ecosystem components potentially resulting in trophic amplification. Trophic amplification (or attenuation) describe the propagation of a hydroclimatic signal up the food web, causing magnification (or depression) of biomass values along one or more trophic pathways. We have employed 3-D coupled physical-biogeochemical models to explore ecosystem responses to climate change with a focus on trophic amplification. The response of phytoplankton and zooplankton to global climate-change projections, carried out with the IPSL Earth System Model by the end of the century, is analysed at global and regional basis, including European seas (NE Atlantic, Barents Sea, Baltic Sea, Black Sea, Bay of Biscay, Adriatic Sea, Aegean Sea) and the Eastern Boundary Upwelling System (Benguela). Results indicate that globally and in Atlantic Margin and North Sea, increased ocean stratification causes primary production and zooplankton biomass to decrease in response to a warming climate, whilst in the Barents, Baltic and Black Seas, primary production and zooplankton biomass increase. Projected warming characterized by an increase in sea surface temperature of 2.29 ± 0.05 °C leads to a reduction in zooplankton and phytoplankton biomasses of 11% and 6%, respectively. This suggests negative amplification of climate driven modifications of trophic level biomass through bottom-up control, leading to a reduced capacity of oceans to regulate climate through the biological carbon pump. Simulations suggest negative amplification is the dominant response across 47% of the ocean surface and prevails in the tropical oceans; whilst positive trophic amplification prevails in the Arctic and Antarctic oceans. Trophic attenuation is projected in temperate seas. Uncertainties in ocean plankton projections, associated to the use of single global and regional models, imply the need for caution when extending these considerations into higher trophic levels.

Scale dependency of insect assemblages in response to landscape pattern

Patches and their boundaries are sensitive to the scale at which they are viewed. The response of species to patchiness may depend on the resolution and on the extent by which the spatial pattern is perceived. The goal of this paper is to identify the scale at which forest spatial pattern causes changes in species richness and abundances of Dipteran and Homopteran species as a whole, and further on their distinctive ecological functional groups. Using remotely-sensed optical imagery, we described the landscape structure surrounding sampling sites. We used two approaches to deal with the problem of the scale of observation: 1) variation of extent using a multiscale analysis, and 2) comparison of two satellite sensors with different spatial resolutions (SPOT: 20 × 20 m, and Landsat TM: 30 × 30 m). The relationship between entomological data and landscape descriptors at different spatial scales was tested with the Mantel test, redundancy analysis and stepwise multiple linear regression. Relative abundances of Homopteran species were affected by landscape patterns at finer scales than in Diptera. The strength of response to landscape was different for each Dipteran functional group. The multiscale analysis also enabled the optimal scale (6.25 ha) of landscape pattern, accounting for 62% of the variation in Homopteran richness, to be identified. As a practical application, Homopteran richness was mapped by extrapolation of the regression function to the pixels of the image. Multiscale analysis provides an alternative view of fragmentation effects, which are traditionally studied through the patch-based approach, and highlights the importance of scale in ecological processes. The detection of optimal scales and the use of satellite images enable maps of important biotic indicators to be drawn up.

Water quality assessment using satellite-derived chlorophyll-a within the European directives, in the southeastern Bay of Biscay

The implementation of water quality European Directives requires an intensification of water quality monitoring, within the limits of the Exclusive Economic Zone. Remote sensing technologies can provide a valuable tool for frequent, synoptic, water-quality observations, over large areas. The aim of this study is to assess the ecological status of Basque coastal water bodies using satellite imagery from MODIS sensor, together with optical and chlorophyll-ain situ measurements. Thus, sea surface satellite-derived chl-a algorithms, the OC3 M, OC5 and a Local empirical algorithm, were compared against in situ measurements using satellite in situ match-ups, 90th Percentile (P90) monthly values for the 2005-2010 period. The OC5 algorithm corresponded most accurately with in situ measurements performed in the area, hence, it was selected. A P90 chlorophyll-a map was created with this algorithm to apply the classification scheme required by the directives. The classification of water bodies, based upon satellite-derived chlorophyll-a, could improve considerably the assessment of water quality.

A Marine Spatial Planning Approach to Select Suitable Areas for Installing Wave Energy Converters (WECs), on the Basque Continental Shelf (Bay of Biscay)

Recently, considerable interest has been generated in the wave energy production. As a new use of the ocean, a Spatial Planning approach is proposed to provide a mechanism to achieve consensus among the sectors operating at present, together with the identification of the most suitable locations to accommodate the Wave Energy Converters (WECs), in the near future. In this contribution: (a) a methodology for the establishment of a Suitability Index (SI) for WECs installation location selection is proposed; (b) the spatial distribution of the SI is mapped; and finally, (c) the accessible wave energy potential has been calculated for the entire Basque continental shelf. As the SI represents the appropriateness of several locations for WECs installation, while minimizing the conflict with other marine uses, the first step in the development of the analysis involved gathering all such information that may be likely to determine, or influence, the decision-making process. Seventeen information layers (among them 10 technical, 4 environmental, and 3 socioeconomical), corresponding to the identified key factors, including the theoretical wave energy in the study area, were generated to define their spatial distribution. Geographical Information System algorithms were used then in the assessment of the total theoretical energy potential and the accessible theoretical energy potential; these were calculated excluding areas where conflicts with other uses occur, such as navigation regulations or designated Marine Protected Areas. The resulting map indicates that, taking into account the zones not affected by “use conflicts,” together with the estimated energy performance of the most advanced WECs technology, the potential energy produced in the study area could supply between 37% and 50% of the electrical consumption of households in the Basque Country. This contribution could avoid the annual emission of 0.96 to 1.54 million tons of CO2 into the atmosphere.

Restoring fish ecological quality in estuaries: Implication of interactive and cumulative effects among anthropogenic stressors.

Estuaries are subjected to multiple anthropogenic stressors, which have additive, antagonistic or synergistic effects. Current challenges include the use of large databases of biological monitoring surveys (e.g. the European Water Framework Directive) to help environmental managers prioritizing restoration measures. This study investigated the impact of nine stressor categories on the fish ecological status derived from 90 estuaries of the North East Atlantic countries. We used a random forest model to: 1) detect the dominant stressors and their non-linear effects; 2) evaluate the ecological benefits expected from reducing pressure from stressors; and 3) investigate the interactions among stressors. Results showed that largest restoration benefits were expected when mitigating water pollution and oxygen depletion. Non-additive effects represented half of pairwise interactions among stressors, and antagonisms were the most common. Dredged sediments, flow changes and oxygen depletion were predominantly implicated in non-additive interactions, whereas the remainder stressors often showed additive impacts. The prevalence of interactive impacts reflects a complex scenario for estuaries management; hence, we proposed a step-by-step restoration scheme focusing on the mitigation of stressors providing the maximum of restoration benefits under a multi-stress context.

A Dark Hole in Our Understanding of Marine Ecosystems and Their Services: Perspectives from the Mesopelagic Community

In the face of increasing anthropogenic pressures acting on the Earth system, urgent actions are needed to guarantee efficient resource management and sustainable development for our growing human population. Our oceans - the largest underexplored component of the Earth system - are potentially home for a large number of new resources, which can directly impact upon food security and the wellbeing of humanity. However, the extraction of these resources has repercussions for biodiversity and the oceans ability to sequester green house gases and thereby climate. In the search for “new resources” to unlock the economic potential of the global oceans, recent observations have identified a large unexploited biomass of mesopelagic fish living in the deep ocean. This biomass has recently been estimated to be 10 billion metric tonnes, 10 times larger than previous estimates however the real biomass is still in question. If we are able to exploit this community at sustainable levels without impacting upon biodiversity and compromising the oceans’ ability to sequester carbon, we can produce more food and potentially many new nutraceutical products. However, to meet the needs of present generations without compromising the needs of future generations, we need to guarantee a sustainable exploitation of these resources. To do so requires a holistic assessment of the community and an understanding of the mechanisms controlling this biomass, its role in the preservation of biodiversity and its influence on climate as well as management tools able to weigh the costs and benefits of exploitation of this community.

Gall wasps and their parasitoids in cork oak fragmented forests

Abstract 1. This paper explores the potential effects of host‐plant fragmentation on cork oak gall wasp populations (Cynipidae, Hymenoptera) and on their predators, lethal inquilines, and parasitoids. To address this objective, galls were collected across a gradient of cork oak (Quercus suber) forest fragmentation in the East Pyrenees (Albera, Spain), and they were incubated to obtain the parasitism rates.

Dispersal similarly shapes both population genetics and community patterns in the marine realm

Dispersal plays a key role to connect populations and, if limited, is one of the main processes to maintain and generate regional biodiversity. According to neutral theories of molecular evolution and biodiversity, dispersal limitation of propagules and population stochasticity are integral to shaping both genetic and community structure. We conducted a parallel analysis of biological connectivity at genetic and community levels in marine groups with different dispersal traits. We compiled large data sets of population genetic structure (98 benthic macroinvertebrate and 35 planktonic species) and biogeographic data (2193 benthic macroinvertebrate and 734 planktonic species). We estimated dispersal distances from population genetic data (i.e., FST vs. geographic distance) and from β-diversity at the community level. Dispersal distances ranked the biological groups in the same order at both genetic and community levels, as predicted by organism dispersal ability and seascape connectivity: macrozoobenthic species without dispersing larvae, followed by macrozoobenthic species with dispersing larvae and plankton (phyto- and zooplankton). This ranking order is associated with constraints to the movement of macrozoobenthos within the seabed compared with the pelagic habitat. We showed that dispersal limitation similarly determines the connectivity degree of communities and populations, supporting the predictions of neutral theories in marine biodiversity patterns.

'The past is the future of the present': Learning from long-time series of marine monitoring.

Using a long-term (1995-2014) monitoring network, from 51 sampling stations in estuaries and coasts of the Basque Country (Bay of Biscay), the objective of this investigation was to assess the responsiveness of 83 variables in water (18), sediments (27), biota (26), phytoplankton (2), macroinvertebrates (5) and fishes (5) to different human pressures and management actions. We used a total of 3247 series of data to analyse trends of improvement and worsening in quality. In a high percentage of the cases, the management actions taken have resulted in positive effects in the environment, as shown by the trend analysis in this investigation. Overall, much more trends of improvement than of worsening have been observed; this is true for almost all the media and biological components studied, with the exception of phytoplankton; and it applies as well to almost all the stations and water bodies, with the exception of those corresponding to areas with water treatment pending of accomplishment. In estuaries with decreasing human pressures during the period, the percentage of series showing quality improvement was higher (approx. 30%) than those showing worsening of quality (12%). Moreover, in those water bodies showing an increase of pressure, variables which can be considered indicators of anthropogenic effects showed negative trends (quality worsening). On the other hand, some of the variables analysed were more affected by natural variability than by changes in pressures. That was the case of silicate, nitrate and suspended solids, which followed trends correlated to salinity, which, in turn, was related to the rainfall regime during the study period.

Characterizing human-modelled landscapes at a stationary state: a case study of Minorca, Spain

The island of Minorca, Spain, has become a patchy mosaic landscape as a result of centuries of human-induced fragmentation. The dynamics of the landscape elements and the spatial pattern of Minorca were analysed to test whether this human-modelled landscape was at a stationary state, and, if it was the case, to see whether the system could be characterized by a particular spatial pattern. Landsat TM satellite images were processed to derive land cover classification and vegetation index maps corresponding to the years 1984 and 1992, the best compromise between null cloudiness and maximum time span. The classification was used to test the stationary state by estimating the transition matrix of land cover. The Normalized Difference Vegetation Index (NDVI) was used to analyse the spatial pattern of change at the patch level. The spatial analysis of NDVI was based on four indices: fractal dimension, number and size distribution of patches, and spatial Kappa index. Those pattern descriptors were compared with values obtained from stochastic landscape simulations. Temporal analysis showed that land cover proportions remained approximately constant over the 8-year period, although interchange amongst patches existed. This suggested that the landscape of Minorca was close to a stationary state. The study of NDVI changes revealed that the spatial structure was different from that of neutral models and presented scale invariance properties. Results from land cover transitions and from NDVI patterning suggest that the landscape of Minorca is a critical system, in the framework of the self-organized criticality hypothesis, i.e. the mosaic of patches would self-organize at the frontier of a dynamic equilibrium constituted by the balance between disturbances and successional processes.