During the summer, the relative influence of resident Atlantic Waters (AW) and new AW largely drives the mesoscale dynamics around the Balearic Islands (NW Mediterranean). Two principal summer hydrographic scenarios were identified in the region, differentiated by the relative position of the density front between new and resident AW within the archipelago and its associated mesoscale activity. In this study, we investigated how those early summer mesoscale scenarios influence larval fish assemblages, by analyzing data from two cruises representative of these two scenarios (2004 and 2005). Redundancy analysis was used to assess the variance in the larval fish assemblage that could be significantly explained by the most parsimonious combination of available environmental variables in both years. While depth was the most important variable in explaining the larval fish assemblage structure variability observed under both scenarios, indicators of mesoscale activity (dynamic height, geostrophic velocity) contributed significantly to understanding the dynamics of the larval fish community. Mesoscale activity was higher in summer 2004, leading to higher larval fish abundances and zooplankton biomass and lower larval fish diversity than in the unusually warm summer 2005, which showed lower mesoscale activity. The larval assemblage dynamics are discussed in terms of extrinsic and species-specific factors.
Human Impacts on the Environment
A report released today by the UN Environment Programme (UNEP) on the occasion of World Oceans' Day recommends a precautionary approach toward microplastic management, with an eventual phase-out and ban of their use in personal care products and cosmetics (PCCP).
The study, entitled Plastic in Cosmetics: Are We Polluting the Environment Through our Personal Care: Plastic ingredients that contribute to marine microplastic litter' is a compilation of currently available knowledge on the linkages between cosmetics and plastic pollution in the oceans.
For the last 50 years, microparticles of plastic, called microplastics, have been used in personal care products and cosmetics (PCCP), replacing natural options in a large number of cosmetic and personal care formulations. Washed down the drain, those particles cannot be collected for recycling, nor do they decompose in wastewater treatment facilities, inevitably ending up in the global ocean, where it fragments and remains.
Although northern bottlenose whales were the most heavily hunted beaked whale, we have little information about this species in its remote habitat of the North Atlantic Ocean. Underwater anthropogenic noise and disruption of their natural habitat may be major threats, given the sensitivity of other beaked whales to such noise disturbance. We attached dataloggers to 13 northern bottlenose whales and compared their natural sounds and movements to those of one individual exposed to escalating levels of 1–2 kHz upsweep naval sonar signals. At a received sound pressure level (SPL) of 98 dB re 1 μPa, the whale turned to approach the sound source, but at a received SPL of 107 dB re 1 μPa, the whale began moving in an unusually straight course and then made a near 180° turn away from the source, and performed the longest and deepest dive (94 min, 2339 m) recorded for this species. Animal movement parameters differed significantly from baseline for more than 7 h until the tag fell off 33–36 km away. No clicks were emitted during the response period, indicating cessation of normal echolocation-based foraging. A sharp decline in both acoustic and visual detections of conspecifics after exposure suggests other whales in the area responded similarly. Though more data are needed, our results indicate high sensitivity of this species to acoustic disturbance, with consequent risk from marine industrialization and naval activity.
Here we present first observations, from instrumentation installed on moorings and a float, of unexpectedly low (<2 μmol kg−1) oxygen environments in the open waters of the tropical North Atlantic, a region where oxygen concentration does normally not fall much below 40 μmol kg−1. The low-oxygen zones are created at shallow depth, just below the mixed layer, in the euphotic zone of cyclonic eddies and anticyclonic-modewater eddies. Both types of eddies are prone to high surface productivity. Net respiration rates for the eddies are found to be 3 to 5 times higher when compared with surrounding waters. Oxygen is lowest in the centre of the eddies, in a depth range where the swirl velocity, defining the transition between eddy and surroundings, has its maximum. It is assumed that the strong velocity at the outer rim of the eddies hampers the transport of properties across the eddies boundary and as such isolates their cores. This is supported by a remarkably stable hydrographic structure of the eddies core over periods of several months. The eddies propagate westward, at about 4 to 5 km day−1, from their generation region off the West African coast into the open ocean. High productivity and accompanying respiration, paired with sluggish exchange across the eddy boundary, create the "dead zone" inside the eddies, so far only reported for coastal areas or lakes. We observe a direct impact of the open ocean dead zones on the marine ecosystem as such that the diurnal vertical migration of zooplankton is suppressed inside the eddies.
Dams are a major contributor to the historic decline and current low abundance of diadromous fish. We developed a population viability analysis to assess demographic effects of dams on diadromous fish within a river system and demonstrated an application of the model with Atlantic salmon in the Penobscot River, Maine. We used abundance and distribution of wild- and hatchery-origin adult salmon throughout the watershed as performance metrics. Salmon abundance, distribution to upper reaches of the Penobscot watershed, and the number and proportion of wild-origin fish in the upper reaches of the Penobscot watershed increased when dams, particularly mainstem dams, were removed or passage efficiency was increased. Salmon abundance decreased as indirect latent mortality per dam was increased. Salmon abundance increased as marine or freshwater survival rates were increased, but the increase in abundance was larger when marine survival was increased than when freshwater survival was increased. Without hatchery supplementation, salmon abundance equalled zero with low marine and freshwater survival but increased when marine and freshwater survival rates were increased. Models, such as this one, that incorporate biological, environmental, and functional parameters can be used to predict ecological responses of fish populations and can help evaluate and prioritize management and restoration actions for diadromous fish.
Foreign fisheries massively harvest waters off West Africa, plundering local marine economies and threatening African food security. Here we warn that these fisheries might affect both juvenile and adult European seabirds during their autumn migration and at their wintering grounds. Using miniaturised GPS, satellite transmitters and geolocators, we tracked the migratory movements of 64 adult and juvenile Northern gannets (Morus bassanus) and Scopoli’s shearwaters (Calonectris diomedea) after their breeding season in the eastern Atlantic and the Mediterranean Sea, respectively. It was the first time ever that the movements of gannet fledglings were tracked with GPS accuracy. During winter (October to March) birds made extensive use of marine areas within the exclusive economic zones of Morocco, Western Sahara, Mauritania and Senegal. These juvenile and adult European seabirds are therefore dependent upon African marine resources and at risk from competition with fisheries, as well as intentional and incidental mortality by fishing gear. Those threats occur additionally to detrimental seabird–fishery interactions in Europe. There is an urgent need for improved marine conservation off West Africa, and our data demonstrating connectivity between specific European breeding colonies and African wintering areas are a major step towards stakeholder involvement.
Wildfire is a common disturbance that can significantly alter vegetation in watersheds and affect the rate of sediment and nutrient transport to adjacent nearshore oceanic environments. Changes in runoff resulting from heterogeneous wildfire effects are not well-understood due to both limitations in the field measurement of runoff and temporally-limited spatial data available to parameterize runoff models. We apply replicable, scalable methods for modeling wildfire impacts on sediment and nonpoint source pollutant export into the nearshore environment, and assess relationships between wildfire severity and runoff. Nonpoint source pollutants were modeled using a GIS-based empirical deterministic model parameterized with multi-year land cover data to quantify fire-induced increases in transport to the nearshore environment. Results indicate post-fire concentration increases in phosphorus by 161 percent, sediments by 350 percent and total suspended solids (TSS) by 53 percent above pre-fire years. Higher wildfire severity was associated with the greater increase in exports of pollutants and sediment to the nearshore environment, primarily resulting from the conversion of forest and shrubland to grassland. This suggests that increasing wildfire severity with climate change will increase potential negative impacts to adjacent marine ecosystems. The approach used is replicable and can be utilized to assess the effects of other types of land cover change at landscape scales. It also provides a planning and prioritization framework for management activities associated with wildfire, including suppression, thinning, and post-fire rehabilitation, allowing for quantification of potential negative impacts to the nearshore environment in coastal basins.
The Tupinambás Ecological Station (TES) is a Marine Protected Area consisting of two sectors: the Archipelago of Alcatrazes and the Cabras and Palmas islets. This investigation aimed to provide a first diagnosis of the concentrations of metals (Al, Cr, Cu, Fe, Hg, Ni, Pb, Zn), As and P in sediments from the TES. 24 sediment samples were collected in both sectors using a Van Veen grab sampler. Sediment textures and levels of Organic Matter (OM) and CaCO3 were determined, as well as the concentrations of the above-mentioned elements after partial acid digestion. Sediments were predominantly sandy. Higher levels of CaCO3 occurred in the Alcatrazes sector, whereas the OM contents were higher in the islets sector. Metals concentrations were low and associated with fines, while P and As presented a different behavior. The observed concentrations to all studies elements in sediments from the TES were considered as background values.
Concerns are growing at multiple levels of government about the effects of ocean acidification and increasing hypoxia events on ecosystems along the coasts of California, Oregon, Washington, and British Columbia. Thoughtful and strategic research and monitoring will be essential to improve understanding of these impacts and to develop effective management and mitigation options.
This report seeks to assist decision-makers across the public sector in supporting science to address ocean acidification and hypoxia. Working with the West Coast Ocean Acidification and Hypoxia Science Panel and other thought leaders, the California Ocean Science Trust has developed this vision for the future state of knowledge and role of science in improving our ability to understand and manage these threats on the West Coast.