Towards improved socio-economic assessments of ocean acidification’s impacts

Ocean acidification is increasingly recognized as a component of global change that could have a wide range of impacts on marine organisms, the ecosystems they live in, and the goods and services they provide humankind. Assessment of these potential socio-economic impacts requires integrated efforts between biologists, chemists, oceanographers, economists and social scientists. But because ocean acidification is a new research area, significant knowledge gaps are preventing economists from estimating its welfare impacts. For instance, economic data on the impact of ocean acidification on significant markets such as fisheries, aquaculture and tourism are very limited (if not non-existent), and non-market valuation studies on this topic are not yet available. Our paper summarizes the current understanding of future OA impacts and sets out what further information is required for economists to assess socio-economic impacts of ocean acidification. Our aim is to provide clear directions for multidisciplinary collaborative research.     

Can leftovers from predators be reliably used to monitor marine turtle hatchling sex-ratios? The implications of prey selection by ghost crabs

In marine turtles, the sex of an individual is determined by temperatures experienced during embryonic development. Gonad histological observation is still the only reliable way to determine hatchling sex, hampering the study of reproduction and of the demographic consequences of context-dependent sex-ratios, a subject of interest in a warming planet. We investigated whether hatchling remains from predation by Ocypode cursor can be used to estimate sex-ratio trends in a green turtle rookery at Poilão, Guinea-Bissau (10°52′N, 15°43′W). Sex could be readily determined in 77 and 79% of the predated hatchlings in 2008 and 2009, respectively. By comparing hatchlings killed by crabs, hatchlings accidentally dying on the reefs, and live hatchlings, we show that ghost crabs select the smaller prey, but do not select according to hatchling sex, which is explained by the lack of hatchling size dimorphism in this population. The proportion of male hatchlings was 0.45 ± 0.06 and 0.15 ± 0.06 for early and late-season clutches, respectively, these differences most likely being explained by rainfall. Using leftovers from predation by crabs may be a good solution to non-invasively monitor broad trends in sex-ratios of sea turtles.     

Diet of juvenile green turtles (<Emphasis Type="Italic">Chelonia mydas</Emphasis>) associating with artisanal fishing traps in a subtropical estuary in Brazil

The diet of 50 juvenile green turtles Chelonia mydas live-captured incidentally by fixed fishing traps between January and June 2009 in Cananéia Estuarine–Lagoon complex, Brazil, was studied through analysis of esophageal lavage samples. Green turtles consumed an omnivorous diet, with 18 food components identified and grouped into 4 categories as follows: terrestrial plants, algae, invertebrates, and seagrass. Black mangrove leaves were of the greatest importance to diet. Turtles incidentally get into fixed traps probably because these devices are located on mangrove margins, where they forage. The additional foods suggest that green turtles also feed opportunistically on material adhered to the trap structure and/or on items that cross into its interior. Green turtle diet in estuarine environments appears to be determined by the availability of food components, with some selectivity toward items of apparently greater nutritional value.     

Measurement of sustainability performance in Brazilian organizations

In recent years, sustainability issues are gaining greater prominence among organizations and their stakeholders around the world. This paper aims to verify the sustainability performance of Brazilian organizations in performance measures and to propose sustainable guidelines with the intention of directing future efforts to the transition to sustainable development. The research utilized a triangulated approach by collecting qualitative and quantitative data acquired through multiple collection methods of a theoretical literature review, documentary analysis of corporate reports, questionnaire survey and semi-structured interviews with industry professionals and academic researchers. The results show that internal organizational factors are the main inductors of the sustainable environment in organizations, and sustainability must be tied to strategic planning, starting from upper management to lower levels. It is essential to use sustainable performance measurement systems in order to respond to external and internal levers and serve as benchmarking for future corporate operations and strategies. In addition, it is the responsibility of organizations to focus their efforts on environmental protection, reduction of energy, corporate reputation, quality management, customer satisfaction and investor relations, as they are considered to be more important and have a relationship of dependence on organizational sustainability. The findings will be of value to professionals and academics who want to start measuring and for continuously improving the sustainability performance of their organizations according to the technical, economic, environmental, social and governance dimensions. This research work also helps to understand the perceptions and expectations of stakeholders.     

Patterns of shelter usage and social aggregation by the vocal Lusitanian toadfish

In some marine fishes, males migrate from deeper to littoral water to breed, where they defend nests and provide parental care. In this study, we describe seasonal patterns of shelter occupation in estuarine shallow waters and assess social aggregation in the Lusitanian toadfish (Batrachoididae), a vocal species with male parental care. Occupation of intertidal shelters was restricted to the breeding season but adult fish remained in subtidal regions during the non-reproductive season and they produced sounds throughout the year. Intertidal shelters were aggregated with up to five shelters found per 2-m segment of an 80-m transect. This aggregation probably resulted from social attraction since many segments were found unoccupied. Moreover, shelters contained on average two fish (maximum of nine). Based on size, shelters with multiple fish seemed to contain females, or possibly sneakers, but also more than one type I male inside, indicating a high social tolerance for conspecifics.     

Modelling the effects of extreme events on the dynamics of the amphipod Corophium orientale

The brackish water amphipod Corophium orientale is the dominant macroinvertebrate species in the upper Mira estuary, a small mesotidal system located in the southwest coast of Portugal. As climate changes will increase the frequency and intensity of extreme events such as floods and droughts, these will have a negative effect on benthic estuarine invertebrates, namely C. orientale. In order to understand the effects of these events on C. orientale, a dynamic model, based on published information and calibrated with field data, was developed and different scenarios were tested.For model construction, the annual development of three cohorts of C. orientale, their growth rates, and the establishment of the timing of each cohort rise and extinction are introduced. This structure can be repeated indefinitely, for years, and few parameters are required. The model simulations highlight the need for refuge areas that enable a fast recovery of the amphipod population after an extreme event and the recolozination of the affected areas.     

Egg release and settlement patterns of dioecious and hermaphroditic fucoid algae during the tidal cycle

The timing of gamete release by fucoid algae, although known to be restricted to calm days is not clearly understood within a circadian time scale. The need for externally fertilizing species to avoid gamete dilution suggests that in wave-exposed areas spawning may occur during particular tidal phases. However, this may differ between mating systems, as selfing species may be less affected by gamete dilution. In this study, two different approaches were used to determine when egg release occurs during the tidal cycle in two sister species with different mating systems. First, egg settlement of Fucus vesiculosus (dioecious) and Fucus spiralis (selfing hermaphrodite) was quantified on removable substrates (egg settlement disks) every day for 2 months and settlement patterns were used to statistically estimate the radius of a circle that would encompass 99% of each patch of settled eggs (the egg dispersal radius). Also, egg release was quantified every 2 h during the tidal cycle. A significantly larger egg dispersal radius (P < 0.02) was found for F. spiralis than F. vesiculosus, and this difference was somewhat site dependent with a greater difference between species in exposed sites. The egg dispersal radius was negatively correlated with significant wave height and positively correlated with sea surface temperature for both the species (P < 0.05), with a greater effect of both the factors for F. spiralis than for F. vesiculosus. Egg release during the tidal cycle was variable between species and experiments, with F. vesiculosus releasing more eggs, later in the day, and at a lower tide, than F. spiralis, which released fewer eggs, throughout the day and at all tides. The dioecious species, F. vesiculosus, may have developed a specific adaptation for timing the egg release to periods when emersed in exposed habitats to avoid rapid dilution of gametes that require outcrossing for fertilization. On the other hand, egg release for F. spiralis, which can self-fertilize, occurred both when emersed and immersed, suggesting this species has developed less synchrony with specific environmental factors. Site dependence also suggests local wave conditions can modulate timing of release. The data are consistent with the relaxation of the selective constraints of water motion on fertilization success in a selfing hermaphrodite, relative to an obligate outcrossing species. Results support the idea that species with different mating systems evolve different sensitivities to environmental cues for gamete release with specific implications for inbreeding and successful external fertilization in the ocean.     

Mortality of large trees and lianas following experimental drought in an Amazon forest

Severe drought episodes such as those associated with El Ni?o Southern Oscillation (ENSO) events influence large areas of tropical forest and may become more frequent in the future. One of the most important forest responses to severe drought is tree mortality, which alters forest structure, composition, carbon content, and flammability, and which varies widely. This study tests the hypothesis that tree mortality increases abruptly during drought episodes when plant-available soil water (PAW) declines below a critical minimum threshold. It also examines the effect of tree size, plant life form (palm, liana, tree) and potential canopy position (understory, midcanopy, overstory) on drought-induced plant mortality. A severe, four-year drought episode was simulated by excluding 60% of incoming throughfall during each wet season using plastic panels installed in the understory of a 1-ha forest treatment plot, while a 1-ha control plot received normal rainfall. After 3.2 years, the treatment resulted in a 38% increase in mortality rates across all stems >2 cm dbh. Mortality rates increased 4.5-fold among large trees (>30 cm dbh) and twofold among medium trees (10-30 cm dbh) in response to the treatment, whereas the smallest stems were less responsive. Recruitment rates did not compensate for the elevated mortality of larger-diameter stems in the treatment plot. Overall, lianas proved more susceptible to drought-induced mortality than trees or palms, and potential overstory tree species were more vulnerable than midcanopy and understory species. Large stems contributed to 90% of the pretreatment live aboveground biomass in both plots. Large-tree mortality resulting from the treatment generated 3.4 times more dead biomass than the control plot. The dramatic mortality response suggests significant, adverse impacts on the global carbon cycle if climatic changes follow current trends.     

Habitat structure affects intraguild predation

Intraguild predation is thought to be ubiquitous in natural food webs. Yet, theory on intraguild predation predicts the intraguild prey to persist only under limited conditions. This gap between theory and empirical observations needs scrutiny. One reason might be that theory has focused on equilibrium dynamics and a limited set of species (usually three) that interact in well-mixed populations in unstructured habitats, and these assumptions will often not hold in natural systems. In this review, we focus on the effects of habitat structure on intraguild predation. Habitat structure could reduce encounter rates between predators and prey and could create refuges for prey. In both cases, habitat structure could reduce the strength of intraguild interactions, thereby facilitating species coexistence. A meta-analysis of studies on manipulation of habitat structure shows that intraguild prey indeed suffer less from intraguild predation in structured habitats. This was further confirmed by a meta-analysis in which studies on intraguild predation were classified according to habitat structure. Intraguild predation reduced densities of the intraguild prey significantly more in habitats with little structure than in habitats rich in structure. The effect of intraguild predation on the shared prey was negative, and not significantly affected by habitat structure. We conclude that habitat structure may increase persistence of the intraguild prey by decreasing the strength of the interaction between intraguild predator and intraguild prey.     

Polychaetes associated to a<Emphasis Type="Italic"> Cymodocea nodosa</Emphasis> meadow in the Canary Islands: assemblage structure,temporal variability and vertical distribution compared to other Mediterranean seagrass meadows

The structure, diversity and temporal distribution of the infaunal polychaetes associated with Cymodocea nodosa meadows were studied in Tenerife (Canary Islands). The samples were collected monthly throughout a year, to depths of 13–16 m. The sediment was extracted by means of PVC cores, in which four layers were separated (i.e. 0–5 cm, 5–10 cm, 10–20 cm and 20–30 cm). A total of 1,167 polychaete specimens, belonging to 69 taxa were collected, representing one of the most dominant groups in the benthic assemblage throughout the entire year. The most common families were Syllidae, Paraonidae and Spionidae, both in terms of abundance and species richness. The dominant species were Streptosyllis bidentata, Aricidea assimilis and Exogone parahomoseta mediterranea, representing also the only constant species throughout the year. The highest values of species richness, diversity, equitability and abundance of polychaetes occurred in September. The multifactorial analysis of abundances (i.e. cluster analysis and non-metric, multi-dimensional scaling) indicated temporal segregation of the samples from July, August and September (i.e. the warmest months) with respect to those from the rest of the year, due to structural differences in the assemblage. Polychaete species have been found to a depth of up to 30 cm in the sediment. Nevertheless, most of them (89%) occurred in the upper 5 cm of the sediment, with an increase of specimens in deeper layers in February (i.e. due to sporadic episodes of higher hydrodynamics). To compare the vertical distribution of polychaetes, additional core samples were collected in two seagrass meadows (i.e. C. nodosa and Ruppia cirrhosa) at Ebros Delta (NW Mediterranean); these were separated into five layers (i.e. 0–5 cm, 5–10 cm, 10–15 cm, 15–20 cm, 20–25 cm). The results obtained for the R. cirrhosa meadow (98% of the polychaetes within the upper 5 cm) agree with those for the Canarian C. nodosa meadow, while the polychaetes reached up to 15 cm depth in the Mediterranean C. nodosa meadow (i.e. ~39% between 0 and 5 cm, ~41% between 5 and 10 cm, ~20% between 10 and 15 cm). Our results indicated that the structural characteristics of the assemblages appeared to be more strongly controlled by the combined characteristics of the sediment (i.e. lack of oxygen, granulometry and degree of compaction) than by the seagrass species building the meadow.Communicated by O. Kinne, Oldendorf/Luhe