Functional plant ecology arises, therefore, as an essentially comparative science concerned with the elucidation of the range of variations in functional properties among plants and the search for patterns and functional laws accounting for this variation. The success and the limitations of comparative functional plant ecology depend on the choices of approach made, involving the aims and scope of the comparison, as well as the methods to achieve them. The screening approach may, if pursued further, generate an encyclopedic catalog of details on functional properties of different plants. The quest to describe the diversity of extant plants and the identification of the basic mechanisms that allow them to occupy different environments have shifted scientists' attention from ancient Greece to the present. The plant functions that represent the core of present efforts in functional plant ecology are those by which plants influence ecosystem functions, particularly those that influence the services and products provided by ecosystems.
A quantitative analysis of biomass and cover of both submerged and emergent macrophytes in 139 lakes reported in the literature revealed that biomass and cover of emergent macrophytes are, on average, proportional to the lake area, but that the biomass and cover of submerged plants are proportionally reduced with increasing lake size. Underwater light was found to be the best descriptor of the cover and biomass of submerged plants. Conversely, emergent macrophytes are most strongly affected by lake morphometry, and in particular by its average slope. The predictability of the abundance of emergent and submerged macrophytes from these environmental factors stresses the predominant role that they play in macrophyte ecology and confirms the existence of strong patterns in the abundance of aquatic plants worldwide.
Lagged algal growth responses are argued to be general phenomena occurring, whenever algal growth is enhanced by some growth stimulus, in all aquatic environments supporting planktonic or epiphytic communities. Lag phenomena can be accounted for through a hierarchical conception of microalgal ecology, involving the partition of lagged responses into an 'intrinsic' component, due to biochemical reorganization needed for rapid cell division, and 'extrinsic' component, due to variability in algal growth and loss rates that result in a lag between enhanced cell division and population growth. The plausibility of such an 'extrinsic' lag component was confirmed by simulation modelling, which also revealed that lag duration should decrease exponentially with increasing growth rate, and increase linearly with increasing variability in growth rate. Lag phenomena in algal growth may be of paramount importance in structuring aquatic ecosystems, because it results in the temporal (and spatial, in systems with important advective components) uncoupling between growth stimuli and algal growth. Further, lag phenomena impinge directly upon the interpretation of field data relating algal growth to contemporary environmental conditions.
Research efforts have intensified to foresee the prospects for marine biomes under climate change and anthropogenic drivers over varying temporal and spatial scales. Parallel with these efforts is the utilization of terminology, such as 'ocean acidification' (OA) and 'ocean deoxygenation' (OD), that can foster rapid comprehension of complex processes driving carbon dioxide (CO2 ) and oxygen (O2 ) concentrations in the global ocean and thus, are now widely used in discussions within and beyond academia. However, common usage of the terms 'acidification' and 'deoxygenation' alone are subjective and, without adequate contextualization, have the potential to mislead inferences over drivers that may ultimately shape the future state of marine ecosystems. Here we clarify the usage of the terms OA and OD as global, climate change-driven processes and discuss the various attributes of elevated CO2 and reduced O2 syndromes common to coastal ecosystems. We support the use of the existing terms 'coastal acidification' and 'coastal deoxygenation' because they help differentiate the sometimes rapid and extreme nature of CO2 and O2 syndromes in coastal ecosystems from the global, climate change-driven processes of OA and OD. Given the complexity and breadth of the processes involved in altering CO2 and O2 concentrations across marine ecosystems, we provide a workflow to enable contextualization and clarification of the usage of existing terms and highlight the close link between these two gases across spatial and temporal scales in the ocean. These distinctions are crucial to guide effective communication of research within the scientific community and guide policymakers responsible for intervening on the drivers to secure desirable future ocean states.
Red Sea mangroves occur in an oligotrophic sea without permanent freshwater inputs. Understanding the mechanisms to cope with nutrient limitation is, therefore, important to understand their distribution and nutrient dynamics in coastal ecosystems. We measured total number of meristems to estimate their leaves production and nutrients (N, P, and Fe) as a function of age in Avicennia marina leaves. Then estimated resorption rates; the recovery of nutrients from senescing leaves before they are shed in a total of 91 leaf from four different mangroves stands in the Central Red Sea. We found that the concentration of N and P but not Fe declined with age. Nutrient content also declined in the older leaves with high resorption capacity of 69% and 72% in N and P vs. low resorption of 42% in Fe. The role of Fe resorption is poorly studied in plants, nevertheless, this study could provide an insight into our knowledge of iron resorption in the mangroves, which has never been assessed before. The leaf nutrient export flux from senescing leaves in monospecific stand of Avicennia marina was 9, 0.4 and 1 g m-2 y-1 for N, P and Fe respectively, suggesting mangrove litter-fall to be an important source of bioavailable iron in particular, due to its low resorption, to the adjacent oligotrophic ecosystem.
Only a few decades ago, seagrass ecology was a virtually non-existent field within marine ecology. In the past 30 years or so, this situation has drastically changed. As a recent analysis of published papers by one of us (CMD; Aquatic Botany 65: 7–20) indicates, current publication rates on seagrass ecology in the international scientific literature are at a level of approximately 100 papers per year, and these rates are still increasing. The growing awareness of the role that seagrasses play in ecology, and in the regulation of the biogeochemical cycles of the coastal zones worldwide, undoubtedly does much to stimulate this ongoing expansion of research efforts. The increase in the number of studies also implies that the community of researchers that enters the field of seagrass studies is growing. Besides the scientists, there is also an expanding community of professionals working in governmental and non-governmental organizations in countries all over the world, which in the context of coastal management or conservation issues are actively involved in seagrass matters.
Abstract There is increasing pressure from policymakers for ecologists to generate more detailed ‘attribution’ analyses aimed at quantitatively estimating relative contributions of different driving forces, including anthropogenic climate change ( ACC ), to observed biological changes. Here, we argue that this approach is not productive for ecological studies. Global meta‐analyses of diverse species, regions and ecosystems have already given us ‘ very high confidence’ [ sensu Intergovernmental Panel on Climate Change ( IPCC )] that ACC has impacted wild species in a general sense. Further, for well‐studied species or systems, synthesis of experiments and models with long‐term observations has given us similarly high confidence that they have been impacted by regional climate change (regardless of its cause). However, the role of greenhouse gases in driving these impacts has not been estimated quantitatively. Should this be an ecological research priority? We argue that development of quantitative ecological models for this purpose faces several impediments, particularly the existence of strong, non‐additive interactions among different external factors. However, even with current understanding of impacts of global warming, there are myriad climate change adaptation options already developed in the literature that could be, and in fact are being, implemented now.
Macroalgal forests export much of their production, partly supporting food webs and carbon stocks beyond their habitat, but evidence of their contribution in sediment carbon stocks is poor. We test the hypothesis that macroalgae contribute to carbon stocks in arctic marine sediments. We used environmental DNA (eDNA) fingerprinting on a large-scale set of surface sediment samples from Greenland and Svalbard. We evaluated eDNA results by comparing with traditional survey and tracer methods. The eDNA-based survey identified macroalgae in 94 % of the sediment samples covering shallow nearshore areas to 1460 m depth and 350 km offshore, with highest sequence abundance nearshore and with dominance of brown macroalgae. Overall, the eDNA results reflected the potential source communities of macroalgae and eelgrass assessed by traditional surveys, with the most abundant orders being common among different methods. A stable isotope analysis showed a considerable contribution from macroalgae in sediments although with high uncertainty, highlighting eDNA as a great improvement and supplement for documenting macroalgae as a contributor to sediment carbon stocks. Conclusively, we provide evidence for a prevalent contribution of macroalgal forests in arctic surface sediments, nearshore as well as offshore, identifying brown algae as main contributors.
Abstract Global losses over the 20th century placed seagrass ecosystems among the most threatened ecosystems in the world, with eutrophication, and associated deterioration of the submarine light environment identified as the main driver. Growing appreciation of the ecological and societal benefits of healthy seagrass meadows has stimulated efforts to protect and restore them, largely focused on reducing nutrient input to coastal waters. Here we analyze a unique data set spanning 135 years on eelgrass ( Zostera marina), the dominant seagrass of the northern hemisphere. We show that meadows in the Western Baltic Sea exhibited major declines relative to historic (1890–1910) reference due to the wasting disease in the 1930s followed by eutrophication peaking in the 1980s, but have only shown modest improvement despite major eutrophication mitigation, halving nitrogen input since the 1980s. Across the past century, we identified generally shallower colonization depths of eelgrass for a given submarine light penetration and, hence, increased apparent light requirements. This suggests that eelgrass recovery is limited by additional stressors. Our study indicates that bottom trawling and intense recent warming (0.5°C per decade, 1985–2018), which impact on deeper and shallower meadows, respectively, suppress eelgrass from fully recovering from eutrophication. Warming is most severe in shallow turbid waters, while clear‐water areas offer eelgrass refugia from warming in deeper, cooler waters; but trawling can prevent eelgrass from reaching these refugia. Efforts to reduce nutrient input and thereby improve water clarity have been instrumental in avoiding a catastrophic loss of eelgrass ecosystems. However, local‐scale future management must, in addition, reduce bottom trawling to facilitate eelgrass reaching deeper, cooler refugia, and increase resilience toward realized and further warming. Warming needs to be limited by meeting global climate change mitigation goals.
The marine realm represents 70% of the surface of the biosphere and contains a rich variety of organisms, including more than 34 of the 36 living phyla, some of which are only found in the oceans. The number of marine species used by humans is growing at unprecedented rates, including the rapid domestication of marine species for aquaculture and the discovery of natural products and genes of medical and biotechnological interest in marine biota. The rapid growth in the human appropriation of marine genetic resources (MGRs), with over 18,000 natural products and 4,900 patents associated with genes of marine organisms, with the latter growing at 12% per year, demonstrates that the use of MGRs is no longer a vision but a growing source of biotechnological and business opportunities. The diversification of the use of marine living resources by humans calls for an urgent revision of the goals and policies of marine protected areas, to include the protection of MGRs and address emerging issues like biopiracy or benefit sharing. Specific challenges are the protection of these valuable resources in international waters, where no universally accepted legal framework exists to protect and regulate the exploitation of MGRs, and the unresolved issues on patenting components of marine life. Implementing steps toward the protection of MGRs is essential to ensure their sustainable use and to support the flow of future findings of medical and biotechnological interest.
