The conservation of British North Sea estuaries

Estuaries are amongst the most productive, but scarce, ecosystems in the world. Britain and the southern North Sea have many and extensive estuaries. Many British North Sea coast estuaries are nationally and internationally important for nature conservation for their variety of sand-dune, saltmarsh, sandflat and mudflat habitats, and the plants and animals that they support. The wildlife of estuaries are currently being affected by a great many of man's activities. Many, particularly land-claim, pollution and recreational activities cause loss and damage to this scarce wildlife habitat. Conservation of British estuaries is achieved mainly through site safeguard — the notification of Sites of Special Scientific Interest (SSSIs) and declaration of National Nature Reserves (NNRs) by the Nature Conservancy Council (NCC), and the designation of sites of international importance under the Ramsar Convention and the EC Directive on Wild Birds — and the amelioration of existing damage by sensitive management and pollution control. Several nationwide surveys, particularly NCC's Estuaries Review, are underway in Britain. These will provide sound comparable information on all estuarine sites, and will form the basis for developing an overall estuarine conservation strategy.     

Ecological assessment of soft bottom benthic communities in northern Spanish estuaries

The implementation of the Water Framework Directive requires the classification of the ecological quality status of benthic macroinvertebrates in costal and transitional waters. The uncertainty and complexity of this task have lead to the creation of specific Geographical Intercalibration Groups (GIGs) for the different ecoregions and types of water bodies established. In this framework, several metrics are under study in the United Kingdom, Spain and Denmark for North East Atlantic coastal waters (NEA-GIG). All of them include in their formulations the AMBI index. Nevertheless, few advances have been made in relation to transitional waters. This paper aims to test the suitability of those methodological procedures for their application in Northern Spanish estuaries. The results show evident divergences in classification of ecological status among methods, although the correlations of corresponding ecological quality ratios (EQRs) are good. Thus, we think that it may be necessary to modify the boundaries between each ecological status category and adjust the reference conditions for the variety of community-types existing in estuarine water bodies. However, some problems arise in the assessment of some naturally stressed communities. In this situation, we found an overall dominance of species tolerant to organic enrichment in all status categories and low range of variation of AMBI index. This aspect introduces some uncertainty in relation to the ability of this index to detect a deleterious effect in these estuarine communities naturally stressed. On the other hand, we found some sites that achieve good status according to the metrics used, even though the number of opportunistic species was high. The use of combined approaches that incorporate physicochemical condition of sediments would be a straightforward approach to reduce the risk of failing in the assignation of ecological status category.     

Water flow and water storage in Agave deserti: osmotic implications of crassulacean acid metabolism

Abstract Water flow and water storage were investigated for Agave deserti, a desert succulent showing crassulacean acid metabolism (CAM). The anatomy and water relations of the peripheral chlorenchyma, where CAM occurs, and the central water-storage parenchyma were investigated for its massive leaves so that these tissues could be incorporated as discrete elements into an electrical-circuit analogue of the whole plant. The daily cycling of osmotic pressure was represented by voltage sources in series with the storage capacitors. With soil water potential and leaf transpiration rate as input variables, axial water flow through the vascular bundles and radial flows into and out of storage during the day/night cycle were determined. The predominantly nocturnal transpiration was coincident with increases in cell osmotic pressure and in titratable acid of the leaf chlorenchyma. In the outer layers of the chlorenchyma, water potential was most negative at the beginning of the night when transpiration was maximum, while the water-storage parenchyma reached its minimal water potential 9 h later. The roots plus stem contributed 7% and the leaves contributed 50% to the total water flow during maximal transpiration; peak water flow from the soil to the roots occurred at dawn and was only 58% of the maximal transpiration rate. Over each 24-h period, 39% of the water lost from the plant was derived from storage, with flow into storage occurring mainly during the daytime. Simulations showed that the acid accumulation rhythm of CAM had little impact on water uptake from the soil under the conditions employed. In the outer chlorenchyma, water potential and water flows were more sensitive to the day/night changes in transpiration than in osmotic pressure. Nevertheless, cell osmotic pressure had a large influence on turgor pressure in this tissue and determined the extent to which storage was recharged during the latter part of the night.     

Ecological assessment criteria for restoring anadromous salmonid habitat in Pacific Northwest estuaries

Restoration of estuarine habitats is essential for the conservation and recovery of depressed Pacific salmon populations. However, assessing the functions of recently restored habitat poses a number of problems because of the transitory occurrence of salmonids in any one location. We propose assessment criteria and metrics that are based on the habitat’s capacity, opportunity, and realized function to enhance survivability of juvenile salmon. Because of the paucity of data relating capacity and opportunity attributes to realized function (e.g. growth, consumption rate, survival), there continues to be a need for manipulative experiments to assess the developmental status of restoration sites. Such a self-monitoring approach of letting the fish diagnose the ecological state of restoration would effectively address the small-scale, site-specific assessment goals and criteria, but ignores the larger-scale issues relating to the ability of diverse salmon species and life histories to occupy estuarine habitat landscapes. If coastal restoration is going to contribute the recovery of anadromous salmonid populations, a landscape perspective is fundamental to restoration planning, implementation, and particularly assessment.     

Terrestrial organic carbon storage in a British moorland

Accurate estimates for the size of terrestrial organic carbon (C) stores are needed to determine their importance in regulating atmospheric CO₂ concentrations. The C stored in vegetation and soil components of a British moorland was evaluated in order to: (i) investigate the importance of these ecosystems for C storage and (ii) test the accuracy of the United Kingdom's terrestrial C inventory. The area of vegetation and soil types was determined using existing digitized maps and a Geographical Information System (GIS). The importance of evaluating C storage using 2D area projections, as opposed to true surface areas, was investigated and found to be largely insignificant. Vegetation C storage was estimated from published results of productivity studies at the site supplemented by field sampling to evaluate soil C storage. Vegetation was found to be much less important for C storage than soil, with peat soils, particularly Blanket bog, containing the greatest amounts of C. Whilst the total amount of C in vegetation was similar to the UK national C inventory's estimate for the same area, the national inventory estimate for soil C was over three times higher than the value derived in the current study. Because the UK's C inventory can be considered relatively accurate compared to many others, the results imply that current estimates for soil C storage, at national and global scales, should be treated with caution.     

Distribution of phytoplankton pigments in nine European estuaries and implications for an estuarine typology

Phytoplankton pigments were studied by LiquidChromatography (HPLC) in nine West Europeanestuaries. Three estuaries, i.e. the Rhine,Scheldt and the Gironde were sampled four timesto cover the different seasons, whereas theother six estuaries were sampled once. Pigmentdistributions in estuaries reflect bothriverine inputs as well as autochthonousblooms. Fucoxanthin was the most commonaccessory photosynthetic pigment showing thatDiatoms were the most common group in thestudied estuaries and were particularlydominant during autumn and winter. In the veryturbid Gironde estuary, degradation processeswere predominant between salinities 1 and 20,while Diatoms, Dinoflagellates and Cryptophytesbloomed above 20 salinity during spring andsummer. This contrasted with the highlyeutrophic but less turbid Scheldt, wherephytoplanktonic blooms occurred at lowsalinities close to the city of Antwerp. In theScheldt, we observed both a tenfold fluctuationof phytoplankton biomass and a fluctuatingpigment diversity index. In contrast,chlorophyll a was always low in theGironde, but we observed large variations ofpigment diversity among samplings duringdifferent seasons. Distribution of pheopigmentsshowed that the maximum turbidity zone (MTZ)was a highly reactive region for heterotrophicphytoplankton degradation. The Scheldt and theThames were the most anthropogenic influencedestuaries contrasting with the Gironde estuarythat has a less urbanised watershed. Anestuarine typology is proposed based on threeclusters emerging from a correspondenceanalysis of pigment variables and variablescharacterising the anthropogenic impact andphysical forcing.     

Ecological change in British broadleaved woodland since 1947

Over the last 60 years Britain's broadleaved woodlands have undergone a complex pattern of ecological change. The total extent has expanded from c . 676 000 ha in 1947 to c . 904 000 ha in 2002, but there has also been significant turnover, with losses of ancient woodland and a gain from new planting. Structural change has occurred due, in part, to change in management. In 1947 21% of the broadleaved resource was classed as coppice, 28% as scrub and only 51% of the area as high forest, compared with 97% high forest in 2002. This has been accompanied by changes in ground flora and the regeneration pattern of tree species, which will impact upon the character of the woodlands. Woods have also become more ecologically isolated because of the decline in semi-natural vegetation in the surrounding countryside, although the long-term impacts of this are poorly understood. Other factors driving ecological change are increased pollution, change in grazing pressures, climate change, alien species and game management. Overall woodland specialist species and those of open habitats tend to be doing less well than woodland generalists. Progress has been made in reversing some adverse impacts such as acid deposition, and action is being taken to reduce the impact of others such as over-grazing by deer. However, some drivers, notably climate change, will be more difficult to address. In the long term integrated management of woods as landscape components whilst meeting economic and societal needs will be required.     

Ecological correlates of seed size in the British flora

1. The association between seed size and habitat shade within the British flora was investigated using a data set of seed masses, life histories and quantitative measures of habitat shade for 504 species; the association between seed size and seed longevity was investigated using a data set of seed masses, life histories and seed longevities for 301 species.
2. The data were analysed using the method of phylogenetically independent contrasts (PICs) calculated using the software package CAIC (Comparative Analysis by Independent Contrasts).
3. Seed mass was found to be positively correlated with habitat shade and negatively correlated with seed longevity, after variation owing to life history had been accounted for.     

A proposed role for inorganic carbon in water oxidation

This is an article on the peroxydicarbonic acid (PODCA) hypothesis of photosynthetic water oxidation, which follows our first article in this general area (Castelfranco et al., Photosynth Res 94:235–246, 2007). In this article I have expanded on the idea of a protein-bound intermediate containing inorganic carbon in some chemically bound form. PODCA is conceived in this article as constituting a bridge between two proteins of the oxygen-evolving complex (OEC) that are essential for the evolution of O₂. Presumably, these are two proteins which have been shown to possess Mn-dependent carbonic anhydrase activity (Lu et al., Plant Cell Physiol 46:1944–1953, 2005; Shitov et al., Biochemistry (Moscow) 74:509–517, 2009). One of these proteins may be the D_I of the OEC core and the other may be the PsbO extrinsic protein. I attempt to relate briefly the PODCA hypothesis to the role of two cofactors for O₂ evolution: Ca²⁺ and inorganic carbon. In this scheme, inorganic carbon (HCO₃ ^?) mediates the oxidation of peroxide to dioxygen, thus avoiding the homolytic cleavage of the peroxide into two free radicals. I visualize the role of Ca²⁺ in the binding of PODCA to two essential photosystem II proteins. I propose that PODCA alternates between two Phases. In Phase 1, PODCA is broken down with the production of O₂. In Phase 2, PODCA is regenerated.     

Mercury concentrations in fish, plankton and water from three Western Atlantic estuaries

Total mercury concentrations were determined in the clupeid, Brevoortia tyrannus , from three estuaries of the Western Atlantic, and in the plankton on which they feed, as well as in the water sampled from the same localities. Although there was some indication that the food chain is a likely source of mercury contamination in these fish, as seen by the very much higher levels found in viscera compared with the rest of the fish, there was no evidence of strong food chain intensification. Fish mercury levels (0.3 to 0.5 part/10⁶ dry wt) were about twice that for plankton (0.1–0.2 part/10⁶ dry wt), with higher levels in phyto-than in zooplankton.     

The management of nutrients and potential eutrophication in estuaries and other restricted water bodies

Conceptual models are derived to indicate the signs and symptoms inherent in nutrient changes to brackish, estuarine and coastal areas of restricted circulation. These give a structured approach to detecting adverse symptoms of hypernutrification and eutrophication at all levels of biological organisation, from effects at cellular levels to the ecosystem approach. The conceptual models illustrate the bottom-up approaches to the detection and control of potential problems and the importance of top-down responses. The bottom-up approaches incorporate mechanisms with regard to inputs, retention of nutrients, biogeochemical cycling and the primary production response. The top-down approaches include the detection of responses in high-profile components of the marine system, such as fisheries, sea mammals and wading birds and seabirds, which are often of paramount socio-economic or conservation importance. The management of the above causes and consequences, and following from the adoption by signatories to proposals given by the Paris Commission (PARCOM), can be accomplished by the derivation of Ecological Quality Objectives (EcoQO) and Ecological Quality Standards (EcoQS). These are given here as a development from the Environmental Quality Objectives and Standards (EQO/EQS) approach. Such EcoQO and EcoQS are regarded as as an aid to monitoring and management of estuaries and coastal waters. That management includes recent proposals within European legislation aimed at monitoring and managing the health and integrity of coasts and estuaries, for example the implementation of the Nitrates, Species & Habitats, and Water Framework Directives. The paper, therefore, discusses both the quality and quantity of data involved in the science required by managers and the way ahead for assessing and managing the fate and effects of nutrients. Using European and U.S. examples, the paper introduces the major challenge of how the concerns highlighted can be addressed by policy action.     

Ecological and evolutionary implications of immunological priming in invertebrates

Invertebrates have an immune response that differs considerably from the acquired immune response found in vertebrates. However, new studies indicate that past experience with a pathogen can provide individual invertebrates, or their descendants, with enhanced immunity. This prophylactic effect, termed immunological priming, is functionally similar to the acquired immune response in vertebrates. This newfound complexity of invertebrate immunity begs investigation into the conditions under which immunological priming should evolve, and its consequences for population dynamics.     

Comparison of various water replenishment and fertilization schemes in brackishwater milkfish ponds

The study was undertaken to determine the optimum combination of the frequency of water replenishment and fertilization that can yield the highest growth, survival, and gross production of milkfish. Results indicated that mean body weight and survival were not significantly different (P > 0.05) among the treatments. Gross fish production was higher in biweekly fertilization if considered as a single factor. However, when this was in combination with the weekly or biweekly water replenishment, similar gross fish production was attained. In any case, because biweekly fertilization has a better effect than a weekly schedule, the former should be used in combination with any other level of replenishment. A weekly water replenishment, however, is impractical in big pond areas of 5–10 ha compartments which are still common in some milkfish ponds in the Philippines. Therefore, biweekly water replenishment and fertilization with 16–20–0 at 50 kg ha^-1 would be reasonable.