Data on hake (Merluccius capensis and Merluccius paradoxus) abundance along the Namibian coast showed both species to have strongly aggregated spatial distributions. In addition, average fish size increased with depth, suggesting that the formation of hake aggregation is based on size-dependent shoaling behaviour. Hake spacing was size dependent with areal fish density and biomass being scaled to the −5 and −2 power, respectively, of fish length. The equations describing the size dependence of the areal fish density were log density (fish∙m −2 ) = 5.06-4.91 log size (cm) for M. capensis and log density (fish∙m −2 ) = 5.28-4.74 log size (cm) for (M. paradoxus). The maximum areal densities, presumably corresponding to those within the shoals, exceeded those described by the equations above by 20- and 13-fold for M. capensis and M. paradoxus, respectively. The size dependence of hake spacing implies that fishing pressure targeting aggregates of small hake (i.e. shallow shoals) should have a disproportionate effect on fish mortality and recruitment compared with similar fishing pressure targeting aggregates of larger hake (i.e. deep shoals).
The role of krill as a source of dissolved organic matter in the Southern Ocean was tested through a series of experiments performed around the Antarctic Peninsula. These experiments revealed high but variable release rates of dissolved material (carbon and nutrients), supplying, on average, 150 mmol dissolved organic carbon (DOC) m −2 d −1 , which is comparable with that supported by phytoplankton. Krill support, on average, 73% of the combined krill + phytoplankton production of DOC in the ecosystem, implying the importance of krill in conditioning the productivity of the Southern Ocean. However, the contribution of krill as a source of DOC varied greatly because of the patchy distribution of both krill and primary producers in the region, ranging from 98% to 10% of the combined (krill + phytoplankton) DOC release rates. These results suggest that rapid decline in krill standing stocks associated with reduced ice cover may have major consequences for microbial communities in the ecosystem, since bacterial carbon demand often exceeds the DOC supplied by phytoplankton in coastal areas of the Southern Ocean, with potential unforeseen consequences in the carbon balance of the Southern Ocean.
An analysis of the contents and conclusions of the papers contained in this issue (Hydrobiologia Volume xxx) suggests that a new vision is taking shape that may correspond to an emerging new paradigm in the way we understand and manage coastal eutrophication. This new paradigm emphasizes its global dimension and the connections with other global environmental pressures, and re-evaluates the targets of remedial actions and policies. Eutrophication research must evolve toward a more integrative, ecosystem perspective which requires that it be extended to include impacts beyond primary producers and to examine possible cascading effects and feedbacks involving other components of the ecosystem. A quantitative framework that incorporates the interacting top-down and bottom-up effects in eutrophication models must be urgently developed to guide diagnostics and establish targets to mitigate coastal eutrophication. The required macroscopic view must also be extended to the managerial and policy frameworks addressing eutrophication, through the development of policies that examine activities in the environment in an integrative, rather than sectorial, manner. Recent evidence of complex responses of coastal ecosystems to nutrient reduction requires that management targets, and the policies that support them, be reconsidered to recognize the complexities of the responses of coastal ecosystems to reduced nutrient inputs, including non-linear responses and associated thresholds. While a predictive framework for the complex trajectories of coastal ecosystems subject to changes in nutrient inputs is being developed, the assessment of managerial actions should be reconsidered to focus on the consideration of the status achieved as the outcome of nutrient reduction plans against that possibly derived from a ‘do nothing’ scenario. A proper assessment of eutrophication and the efforts to mitigate it also requires that eutrophication be considered as a component of global change, in addressing both its causes and its consequences, and that the feedbacks between other components of global change (e.g., climate change, overfishing, altered biogeochemical cycles, etc.) be explicitly considered in designing eutrophication research and in managing the problem.
Patches of Cymodocea nodosa colonizing highly mobile sandy sediments were studied to determine the temporal and spatial course of biomass and demographic development.Results show (1) a close coupling between rhizome growth and shoot density and biomass; (2) an average b ~o n ~a s s accumulation rate of ca 250 g fresh wt m-2 yr-l for rhizomes and 480 g m-2 yr-' for shoots; and (3) a close relationship between plant biomass and distance from patch edge Short shoots are produced in annual cohorts, subject to an average mortality of ca 1.0 exponential unit yr-' regardless of cohort age, but shoot mortality decreases with distance from patch edge.Patch maintenance is achieved by shoot recruitment rates closely matching shoot mortality rates.Mean shoot age, variability in shoot age structure, and associated shoot characteristics (i.e.length and number of standing leaves), increase with time after patch establishment.These results demonstrate the importance of shoot recruitment and mortality for the maintenance and growth of C. nodosa patches and, hence, for seagrass recovery.
This article presents a designed participatory tool to foster sustainable social innovation in rural areas and enhance crafts-based transdisciplinary practices. The proposed method explores the possibilities of a conceptual framework that offers co-creation and community solutions, leveraging the power of crafts, cultural heritage, and local resources. The article presents the methodology and results achieved during three pilot workshops conducted with designers, design students, researchers and other experts during international design research conferences held in Málaga, Valencia and Lisbon between, November 2023 and April 2024. The participatory method emerged from a doctoral research project aimed at promoting sustainable and innovative solutions in rural areas and raising awareness about the role of crafts and design in driving positive change. The objective of the workshop was to test the proposed method and gather insights for applying the tool in real-world scenarios, promoting co-creation practices, and collaborative methodologies in rural areas. The workshop uses a toolkit that includes a canvas and a deck of cards, among other elements. The activity taught participants how to co-design solutions tailored to specific situations considering the crafts, tools, skills, and agents involved. Participants were trained in developing solutions for rural areas that address specific challenges and complex scenarios.