Mariano Lastra

Give Beach Ecosystems Their Day in the Sun

The Intergovernmental Panel on Climate Change Fourth Assessment Report ([ 1 ][1]) largely overlooked the impacts of climate change on marine ecosystems ([ 2 ][2]). In their Review (“The impact of climate change on the worlds marine ecosystems,” 18 June, p. [1523][3]), O. Hoegh-Guldberg and J. F

Burrowing abilities and swash behavior of three crabs, Emerita analoga Stimpson, Blepharipoda occidentalis Randall, and Lepidopa californica Efford (Anomura, Hippoidea), of exposed sandy beaches

To investigate factors related to the distribution of intertidal species, and specific predictions of the swash exclusion hypothesis for exposed sandy beaches, we compared the burrowing abilities and swash behavior of three species of anomuran crabs in the superfamily Hippoidea (Emerita analoga, Blepharipoda occidentalis and Lepidopa californica) which commonly inhabit the intertidal and shallow subtidal zones of beaches along the California coast. Burrowing times in the laboratory increased significantly with crab size for all species in five sediment grain sizes ranging from fine sand to gravel (0.15 to 3.24 mm). For each species, burrowing times differed significantly among sand grain sizes, ranging from 0.3 to 21.5 s. Burrowing times for the hippid crab, E. analoga, were relatively constant across sediment types, while those of the albuneid crabs, B. occidentalis and L. californica, were rapid in fine to medium sands, and much slower in coarser sediments. Our results indicate that E. analoga is a substrate generalist while L. californica and B. occidentalis are substrate sensitive. Pre-burrowing times and behavior, distance moved, and burrowing times differed among the species in the swash zone. Combined times of preburrowing and burrowing were shorter than the swash period (6 s) for most E. analoga individuals. Fifty percent of the individuals of L. californica reached the substrate and burrowed in the swash period, while no individuals of B. occidentalis burrowed in that time. Pre-burrowing behavior and time may be valuable in explaining spatial and temporal patterns in the distribution of hippoid crabs on California beaches. Our results support predictions of the swash exclusion hypothesis concerning the burrowing and locomotory abilities of sandy beach macrofauna. The substrate generalist characteristics, and unique orientation and swimming abilities of the hippid crab, E. analoga, in intertidal swash may help explain the success of this species and its congeners, and have important implications for understanding patterns of macrofauna community structure on exposed sandy beaches in California and other regions.

Meiofauna distribution along a gradient of sandy beaches in northern Spain

Ten sandy beaches located in northern Spain were studied during the summer of 1999 to analyse the patterns in number of major taxa, abundance and biomass of meiofauna along a gradient of morphodynamic beach types and exposure rate. Sediment samples were collected with metallic cylinders (23 cm 2 cross-sectional area, 120 cm long) at 10 equally spaced shore levels along six replicated transects extended from the drift line down to the low tide level. Wave exposure rate and Dean’s parameter were estimated at each sampled beach. The meiofauna was primarily represented by Nematoda and Harpacticoidea. Meiofaunal abundances ranged between 64 � 10 6 and 296 � 10 6 ind. m � 1 , whereas biomass (ash free dry weight) per linear meter of beach ranged between 30 and 166 g m � 1 . The results showed two significant trends: (1) the meiofaunal biomass increases exponentially with exposure rate from exposed to very exposed beaches; and (2) the number of major taxa increases exponentially with exposure rate and linearly with average grain size. These trends are opposite to the general patterns of the sandy beach macroinfauna, which is generally negatively affected by increases in wave exposure and grain size. This suggests that macro- and meiofauna are affected in different ways by the physical processes associated with wave action. 2003 Elsevier Ltd. All rights reserved.

The influence of sediment grain size on burrowing, growth and metabolism of Donax trunculus L. (Bivalvia: Donacidae)

The bivalve Donax trunculus L. commonly inhabits the intertidal and shallow subtidal zone of exposed sandy beaches along European and North African coasts. We examined the responses of burrowing time, respiration rate and growth of this species to sediment grain size. Burrowing time was examined for individuals from 5 to 45 mm shell length in artificially prepared sorted sediments varying from fine sand (125–250 μm) to medium sand (250–500 μm), coarse sand (500–1000 μm), very coarse sand (1000–2000 μm), gravel (>2000 μm), and native sediment (432 μm mean grain size). The shortest burrowing time for individuals between 5 and 25 mm was observed in medium and coarse sands. For individuals of 25–45 mm shell length, the shortest burrowing time occurred in fine and medium sands. The longest burrowing time for all size classes was observed in gravel. These results were analysed within the framework of the swash exclusion hypothesis. According to this hypothesis, burrowing time of D. trunculus in relation to wave period determines to what extent individuals are drifted from the zone where they preferentially live. The shorter burrowing time of smaller clams, and their ability to burrow faster than larger individuals in coarse sands suggest that juveniles may be able to withstand more reflective morphodynamic conditions than adult individuals. Effects of sediment grain size on metabolic activity and growth rates were compared by maintaining D. trunculus (26–28 mm shell length) in different sediment grades. Metabolic activity and growth rate were highest in medium and coarse grades of sand. In gravel and very coarse sand, growth rates and metabolic rates were lower by as much as 43%. Our data indicated that a small decline in metabolism was accompanied by a greater decrease in growth. Thus, our results agree with the swash exclusion hypothesis: the coarsest granulometries, predominant on the reflective type of beaches, reduce the ecological efficiency of individuals by decreasing either their burrowing rate, and/or growth and metabolism.

Metrics to assess ecological condition, change, and impacts in sandy beach ecosystems.

Complexity is increasingly the hallmark in environmental management practices of sandy shorelines. This arises primarily from meeting growing public demands (e.g., real estate, recreation) whilst reconciling economic demands with expectations of coastal users who have modern conservation ethics. Ideally, shoreline management is underpinned by empirical data, but selecting ecologically-meaningful metrics to accurately measure the condition of systems, and the ecological effects of human activities, is a complex task. Here we construct a framework for metric selection, considering six categories of issues that authorities commonly address: erosion; habitat loss; recreation; fishing; pollution (litter and chemical contaminants); and wildlife conservation. Possible metrics were scored in terms of their ability to reflect environmental change, and against criteria that are widely used for judging the performance of ecological indicators (i.e., sensitivity, practicability, costs, and public appeal). From this analysis, four types of broadly applicable metrics that also performed very well against the indicator criteria emerged: 1.) traits of bird populations and assemblages (e.g., abundance, diversity, distributions, habitat use); 2.) breeding/reproductive performance sensu lato (especially relevant for birds and turtles nesting on beaches and in dunes, but equally applicable to invertebrates and plants); 3.) population parameters and distributions of vertebrates associated primarily with dunes and the supralittoral beach zone (traditionally focused on birds and turtles, but expandable to mammals); 4.) compound measurements of the abundance/cover/biomass of biota (plants, invertebrates, vertebrates) at both the population and assemblage level. Local constraints (i.e., the absence of birds in highly degraded urban settings or lack of dunes on bluff-backed beaches) and particular issues may require alternatives. Metrics - if selected and applied correctly - provide empirical evidence of environmental condition and change, but often do not reflect deeper environmental values per se. Yet, values remain poorly articulated for many beach systems; this calls for a comprehensive identification of environmental values and the development of targeted programs to conserve these values on sandy shorelines globally.

Temporal and spatial variability of sedimentary organic matter in sandy beaches on the northwest coast of the Iberian Peninsula

Temporal and spatial changes in sedimentary organic matter have been studied in several localities of the northwest coast of Spain. Biochemical composition of the sedimentary organic matter was studied in August and September 1997 in 10 beaches subjected to a different exposure degree to the wave action. Temporal variations in main biochemical classes were investigated in two of them (the more exposed and the more sheltered) over a 1-year period from January 1997 to January 1998 every 3 months. Sediment samples for the analysis of lipids, proteins and carbohydrates were collected at three tidal levels: high, medium and low, when the tide was on the ebb. Biochemical compounds concentrations were significantly higher in the sheltered beaches than in the exposed ones. The low hydrodynamic conditions of the sheltered beaches favour a high accumulation of sedimentary organic matter. There were significant differences among seasons and tidal levels. The biopolymeric carbon (BPC, i.e. the sum of lipid, protein and carbohydrate carbon) was dominated by proteins, followed by lipids and carbohydrates, pointing out the no limitation for heterotrophic metabolism in intertidal sediments. The exposure degree to the wave action was calculated by means of the beach slope. The relation between this parameter and the biochemical compounds showed that localities with low slopes (i.e. sheltered beaches) were related to high concentrations of lipids, proteins and carbohydrates and vice versa. The three biochemical classes showed different trends with time and changes were more pronounced in the sheltered beach than in the exposed one. These results could be explained by the influence of allochthonous inputs in the sheltered beach, which were not observed in the exposed one.

Macroinfauna community structure and biochemical composition of sedimentary organic matter along a gradient of wave exposure in sandy beaches (NW Spain)

Six sandy beaches on the North West coast of Spain, exposed to different wave action, were sampled in order to study the macroinfauna community and the biopolymeric fraction (proteins, lipids and carbohydrates) of sedimentary organic matter. According to McLachlan’s rating system (1980), three of them were classified as sheltered and the other three as exposed beaches. Sampling was carried out during August 2004 at three tidal levels: high, medium and low. Macroinfauna community and organic matter concentrations were found to be significantly different when sheltered and exposed beaches were compared. Macroinfauna diversity (H′), abundances and biomass became increasingly enriched along a gradient from exposed to sheltered beaches. Macroinfauna mean abundance was found higher in sheltered (ranked from 1535 ± 358 to 15062 ± 5771 ind m−2) than in exposed beaches (from 150 ± 41 to 5518 ± 1986 ind m−2). Macroinfauna biomass ranged from 3.2 to 14.7 g m−2 and species richness from 25 to 27 in sheltered localities; while in exposed beaches, biomass ranged from 0.2 to 2.3 g m−2 and the number of species from 5 to 14. The biopolymeric carbon concentration (BPC) was significantly higher in sheltered (from 84.7 ± 44.7 to 163.3 ± 34.8) than in exposed (from 30.3 ± 7.5 to 78.7 ± 12.3) beaches. The low hydrodynamic conditions of sheltered beaches favoured the settlement of organic rich fine sediments, being supported by the higher protein to carbohydrate ratio found in the exposed (from 23.5 ± 0.9 to 32.7 ± 4.4), rather than in the sheltered localities (from 6.2 ± 0.7 to 13.6). Mean macroinfauna abundances were higher at medium and low tidal levels in both sheltered and exposed beaches. Crustacea was found to be the main group inhabiting the upper part of both types of beaches, dominating all tidal levels of exposed sandy beaches. Mollusca and Polychaeta groups were dominant in sheltered beaches at the medium and lower levels. There was a significant negative relationship between the BPC and the beach face slope; thus, BPC decreased as the intertidal slope increased. It seems that exposed sandy beaches are mainly physically controlled, whereas hospitable sheltered beaches let other factors, such as biochemical compounds, enrich the benthic fauna scenery.

Exploring macroinvertebrate species distributions at regional and local scales across a sandy beach geographic continuum.

Exposed sandy beaches are highly dynamic ecosystems where macroinvertebrate species cope with extremely variable environmental conditions. The majority of the beach ecology studies present exposed beaches as physically dominated ecosystems where abiotic factors largely determine the structure and distribution of macrobenthic communities. However, beach species patterns at different scales can be modified by the interaction between different environmental variables, including biotic interactions. In this study, we examined the role of different environmental variables for describing the regional and local scale distributions of common macrobenthic species across 39 beaches along the North coast of Spain. The analyses were carried out using boosted regression trees, a relatively new technique from the field of machine learning. Our study showed that the macroinvertebrate community on exposed beaches is not structured by a single physical factor, but instead by a complex set of drivers including the biotic compound. Thus, at a regional scale the macrobenthic community, in terms of number of species and abundance, was mainly explained by surrogates of food availability, such as chlorophyll a. The results also revealed that the local scale is a feasible way to construct general predictive species-environmental models, since relationships derived from different beaches showed similar responses for most of the species. However, additional information on aspects of beach species distribution can be obtained with large scale models. This study showed that species-environmental models should be validated against changes in spatial extent, and also illustrates the utility of BRTs as a powerful analysis tool for ecology data insight.

Open-coast sandy beaches and coastal dunes

Coastal ecosystems are centres of high biological productivity, but their conservation is often threatened by numerous and complex environmental factors. Citing examples from the major littoral habitats worldwide, such as sandy beaches, salt marshes and mangrove swamps, this text characterises the biodiversity of coastline environments and highlights important aspects of their maintenance and preservation, aided by the analysis of key representative species. Leaders in the field provide reviews of the foremost threats to coastal networks, including the effects of climate change, invasive species and major pollution incidents such as oil spills. Further discussion underscores the intricacies of measuring and managing coastline species in the field, taking into account the difficulties in quantifying biodiversity loss due to indirect cascading effects and trophic skew. Synthesising the current state of species richness with present and projected environmental pressures, the book ultimately establishes a research agenda for implementing and improving conservation practices moving forward. [Book Synopsis]

Coupling between macroalgal inputs and nutrients outcrop in exposed sandy beaches

Fluxes of nutrients across habitats are of paramount relevance in ecological studies due to the implication in primary production, trophic structure and biodiversity. This study analyses the role of sandy beaches in the processing of organic matter. Three beaches with different macroalgal inputs were sampled throughout the annual cycle. The standing stock of wrack macroalgae on the beach surface and the nutrient concentration in the intertidal pore water (IPW) and in the surf zone water were measured monthly. Mean concentration of dissolved inorganic nitrogen and phosphate in the IPW increased from the low to the very high subsidized beach. Seasonal coupling was observed between the wrack biomass and the nutrient concentration throughout the year. Among the nutrient species, a variable relationship was found between the NH4+/NOx− ratio and the biomass of macroalgae deposited. These results provide evidences of the active role of sandy beaches in the processing of organic matter and in the nutrient cycling, remarking the feedback connectivity between sandy beaches and their neighbour ecosystems.