Marine Benthic Ecosystems Research Articles

Rhodoliths in Brazil: Current knowledge and potential impacts of climate change

Abstract Rhodolith beds are important marine benthic ecosystems, representing oases of high biodiversity among sedimentary seabed environments. They are found frequently and abundantly, acting as major carbonate 'factories' and playing a key role in the biogeochemical cycling of carbonates in the South Atlantic. Rhodoliths are under threat due to global change (mainly related to ocean acidification and global warming) and local stressors, such as fishing and coastal run-off. Here, we review different aspects of the biology of these organisms, highlighting the predicted effects of global change, considering the additional impact of local stressors. Ocean acidification (OA) represents a particular threat that can reduce calcification or even promote the decalcification of these bioengineers, thus increasing the eco-physiological imbalance between calcareous and fleshy algae. OA should be considered, but this together with extreme events such as heat waves and storms, as main stressors of these ecosystems at the present time, will worsen in the future, especially if possible interactions with local stressors like coastal pollution are taken into consideration. Thus, in Brazil there is a serious need for starting monitoring programs and promote innovative experimental infrastructure in order to improve our knowledge of these rich environments, optimize management efforts and enhance the needed conservation initiatives.

Feeding strategies of co-occurring suspension feeders in an oligotrophic environment

Suspension-feeders predominate in the vast majority of the coastal marine benthic ecosystems, with several species co-occurring at low spatial scale. Understanding how these species cope with competition for trophic resources has been the core of numerous studies, mostly in coastal shallow systems where food supplies are diverse and abundant. Oligotrophic systems have received less attention. The aim of the present study was thus to investigate the trophic relationships established between 9 suspension feeders collected in an oligotrophic zone (Bay of Marseille, French Mediterranean). Species displayed similar isotopic ratios, consistently with the use of one main source, identified as nanophytoplankton and diazotrophic bacteria as the δ15N values were low, in contrast to interspecific differences generally observed. The seasonal variations of the isotopic ratios and isotopic niche indices were explained by differential sorting abilities, higher for bivalves than for ascidians and the polychaete Chaetopterus variopedatus. The present results demonstrate that resource availability in oligotrophic systems is a major driver of trophic competition. It precludes a general conclusion about suspension feeders trophic patterns drawn exclusively from highly productive systems, and stresses the need for an extensive assessment of those patterns in a vast range of ecosystems.

SEM study of species of Oswaldella Stechow, 1919 (Cnidaria, Hydrozoa, Kirchenpaueriidae), with an annotated checklist of the species of the genus.

Oswaldella is the most speciose genus, and one of the most characteristic, of hydrozoans inhabiting the Antarctic benthic marine ecosystem. Its species have relatively many important taxonomic characters allowing for their identification. Some of them, however, are difficult to study properly with a compound microscope. With the aim of improving scientific knowledge concerning species of the genus, a SEM survey of species of Oswaldella was carried out to study key morphological characters. Fourteen out of the 27 known nominal species were considered. The study has revealed unknown important characters, such as the presence of nematothecae associated with the nematophores at the cauline apophyses, and has provided a better understanding of others, such as the shape of the nematotheca associated with the medial infrathecal nematophore. A final general discussion on some of the characters studied and on the bathymetrical and geographical distribution of all known species is also included. Finally, an annotated checklist including all known nominal species has also been assembled.

Persistent natural acidification drives major distribution shifts in marine benthic ecosystems.

Ocean acidification is receiving increasing attention because of its potential to affect marine ecosystems. Rare CO2 vents offer a unique opportunity to investigate the response of benthic ecosystems to acidification. However, the benthic habitats investigated so far are mainly found at very shallow water (less than or equal to 5 m depth) and therefore are not representative of the broad range of continental shelf habitats. Here, we show that a decrease from pH 8.1 to 7.9 observed in a CO2 vent system at 40 m depth leads to a dramatic shift in highly diverse and structurally complex habitats. Forests of the kelp Laminaria rodriguezii usually found at larger depths (greater than 65 m) replace the otherwise dominant habitats (i.e. coralligenous outcrops and rhodolith beds), which are mainly characterized by calcifying organisms. Only the aragonite-calcifying algae are able to survive in acidified waters, while high-magnesium-calcite organisms are almost completely absent. Although a long-term survey of the venting area would be necessary to fully understand the effects of the variability of pH and other carbonate parameters over the structure and functioning of the investigated mesophotic habitats, our results suggest that in addition of significant changes at species level, moderate ocean acidification may entail major shifts in the distribution and dominance of key benthic ecosystems at regional scale, which could have broad ecological and socio-economic implications.

Complex metacommunity structure for benthic invertebrates in a low-diversity coastal system.

The majority of studies in metacommunity ecology have focused on systems other than marine benthic ecosystems, thereby providing an impetus to broaden the focus of metacommunity research to comprise marine systems. These systems are more open than many other systems and may thus exhibit relatively less discrete patterns in community structure across space. Metacommunity structure of soft‐sediment benthic invertebrates was examined using a fine‐grained (285 sites) data set collected during one summer across a large spatial extent (1700 km2). We applied the elements of metacommunity structure (EMS) approach, allowing multiple hypothesis of variation in community structure to be tested. We demonstrated several patterns associated with environmental variation and associated processes that could simultaneously assemble species to occur at the sites. A quasi‐Clementsian pattern was observed frequently, suggesting interdependent ecological relationships among species or similar response to an underlying environmental gradient across sites. A quasi‐nested clumped species loss pattern was also observed, which suggests nested habitat specialization. Species richness declined with depth (from 0.5 to 44.8 m). We argue that sensitive species may survive in shallower water, which are more stable with regard to oxygen conditions and present greater habitat complexity, in contrast to deeper waters, which may experience periodic disturbance due to hypoxia. Future studies should better integrate disturbance in terms of temporal dynamics and dispersal rates in the EMS approach. We highlight that shallow water sites may act as sources of recruitment to deeper water sites that are relatively more prone to periodic disturbances due to hypoxia. However, these shallow sites are not currently monitored and should be better prioritized in future conservation strategies in marine systems.

High-throughput sequencing and morphology perform equally well for benthic monitoring of marine ecosystems.

Environmental diversity surveys are crucial for the bioassessment of anthropogenic impacts on marine ecosystems. Traditional benthic monitoring relying on morphotaxonomic inventories of macrofaunal communities is expensive, time-consuming and expertise-demanding. High-throughput sequencing of environmental DNA barcodes (metabarcoding) offers an alternative to describe biological communities. However, whether the metabarcoding approach meets the quality standards of benthic monitoring remains to be tested. Here, we compared morphological and eDNA/RNA-based inventories of metazoans from samples collected at 10 stations around a fish farm in Scotland, including near-cage and distant zones. For each of 5 replicate samples per station, we sequenced the V4 region of the 18S rRNA gene using the Illumina technology. After filtering, we obtained 841,766 metazoan sequences clustered in 163 Operational Taxonomic Units (OTUs). We assigned the OTUs by combining local BLAST searches with phylogenetic analyses. We calculated two commonly used indices: the Infaunal Trophic Index and the AZTI Marine Biotic Index. We found that the molecular data faithfully reflect the morphology-based indices and provides an equivalent assessment of the impact associated with fish farms activities. We advocate that future benthic monitoring should integrate metabarcoding as a rapid and accurate tool for the evaluation of the quality of marine benthic ecosystems.

Is the meiofauna a good indicator for climate change and anthropogenic impacts?

Our planet is changing, and one of the most pressing challenges facing the scientific community revolves around understanding how ecological communities respond to global changes. From coastal to deep-sea ecosystems, ecologists are exploring new areas of research to find model organisms that help predict the future of life on our planet. Among the different categories of organisms, meiofauna offer several advantages for the study of marine benthic ecosystems. This paper reviews the advances in the study of meiofauna with regard to climate change and anthropogenic impacts. Four taxonomic groups are valuable for predicting global changes: foraminifers (especially calcareous forms), nematodes, copepods and ostracods. Environmental variables are fundamental in the interpretation of meiofaunal patterns and multistressor experiments are more informative than single stressor ones, revealing complex ecological and biological interactions. Global change has a general negative effect on meiofauna, with important consequences on benthic food webs. However, some meiofaunal species can be favoured by the extreme conditions induced by global change, as they can exhibit remarkable physiological adaptations. This review highlights the need to incorporate studies on taxonomy, genetics and function of meiofaunal taxa into global change impact research.

Evaluating potential artifacts of tethering techniques to estimate predation on sea urchins

Measuring the strength of trophic interactions in marine systems has been central to our understanding of community structuring. Sea urchin tethering has been the method of choice to evaluate rates of predation in marine benthic ecosystems. As standardly practiced, this method involves piercing the urchin test, potentially introducing significant methodological artifacts that may influence survival or detection by predators. Here we assess possible artifacts of tethering comparing invasive (pierced) and non-invasive tethering techniques using the sea urchin Paracentrotus lividus. Specifically, we looked at how degree of confinement and high water temperature (first order artifacts) and predator guild and size of the prey (second order artifacts) affect the survival and/or detectability of pierced urchins. Our results show that first order artifacts only arise when pierced sea urchins are placed in sheltered bays with confined waters, especially when water temperature reaches extremely high levels. Prey detectability did not increase in pierced sea urchins for the most common predators. Also, test piercing did not alter the preferences of predators for given prey sizes. We conclude that the standard tethering technique is a robust method to test relative rates of sea urchin predation. However, local conditions could increase mortality of the tethered urchin in sheltered bays or in very high temperature regimes. Under these conditions, adequate pierced controls (within predator exclusions) need to be included in assays to evaluate artifactual sources of mortality.

Two episodes of evolution of trace fossils during the Early Triassic in the Guiyang area, Guizhou Province, South China

Abstract The Lower Triassic of the Guiyang area of southern China contains abundant and well-preserved trace fossils, which are useful in the reconstruction of ecological conditions following the end-Permian mass extinction. A total of 16 ichnogenera and 22 ichnospecies were identified; their vertical distribution and evolution indicate that benthic ecosystems experienced two periods of episodic recovery after the P–T event. Episode 1 occurs in the Daye Formation during the Dienerian, when trace-makers first appear in the upper portion of Member D1. Member D2 exhibits the first abrupt increase in ichnodiversity, and trace-makers shift from simple to complex, and undergo a substantial increase in size. These trends indicate a strong capability to rework sediments and an improvement of feeding strategies of trace makers, and points to the development of an early, initial, benthic ecosystem. Despite the emergence of complex trace fossils in D2, such as Phycodes and Phycosiphon , most of the trace fossils are small, horizontal burrows that are not fully developed in three dimensions. By the end of Dienerian, the regional environment deteriorated, and the benthic ecosystem was destroyed, as evidenced by the disappearance of trace fossils from upper D3 to lower A1, which also corresponds to a marked negative shift of δ 13 C carb . As a result, this newly established benthic ecosystem was vulnerable. Episode 2 occurs from the late Smithian to the Spathian. Trace fossils reappear in the lower Anshun Formation. The trace fossils from this stage are larger, more complex, and are fully three-dimensional. Trace maker diversity increases from single polychaeta, followed by the appearance of crustaceans, as represented by Rhizocorallium in Member A3 of the Anshun Formation. During this period, the marine environment improved and benthic organisms gradually established a basis for a new benthic ecosystem. The marine benthic communities had a transformative effect on the ecological environment of the ocean bottom and played an essential role in paving the way for the recovery of other organisms. Two episodes of evolution of trace fossils reflect that initial restoration of benthic ecosystems was apparently reset at least once during the Early Triassic, recovery was not delayed because of persistent environmental stress but short episodes of deleterious conditions. Marine benthic ecosystems had a full and lasting recovery occurred at the global scale during the Spathian, when oceanographic conditions ameliorated and allowed the recovery of ecosystems worldwide.

Was the Ediacaran–Cambrian radiation a unique evolutionary event?

AbstractThe extent of morphologic innovation during the Ediacaran–Cambrian diversification of animals was unique in the history of metazoan life. This episode was also associated with extensive changes in the redox state of the oceans, in the structure of benthic and pelagic marine ecosystems, in the nature of marine sediments, and in the complexity of developmental interactions in Eumetazoa. But did the phylogenetic and morphologic breadth of this episode simply reflect the unusual outcome of recurrent evolutionary processes, or was it the unique result of circumstances, whether in the physical environment, in developmental mechanisms, or in ecological interactions? To better characterize the uniqueness of the events, I distinguish among these components on the basis of the extent of sensitivity to initial conditions and unpredictability, which generates a matrix of possibilities from fully contingent to fully deterministic. Discriminating between these differences is important for informing debates over determinism versus the contingency in the history of life, for understanding the nature of evolutionary theory, and for interpreting historically unique events.

Decline in the species richness contribution of Echinodermata to the macrobenthos in the shelf seas of China

Echinoderms play crucial roles in the structure of marine macrobenthic communities. They are sensitive to excess absorption of CO2 by the ocean, which induces ocean acidification and ocean warming. In the shelf seas of China, the mean sea surface temperature has a faster warming rate compared with the mean rate of the global ocean, and the apparent decrease in pH is due not only to the increased CO2 absorption in seawater, but also eutrophication. However, little is known about the associated changes in the diversity of echinoderms and their roles in macrobenthic communities in the seas of China. In this study, we conducted a meta-analysis of 77 case studies in 51 papers to examine the changes in the contribution of echinoderm species richness to the macrobenthos in the shelf seas of China since the 1980s. The relative species richness (RSR) was considered as the metric to evaluate these changes. Trends analysis revealed significant declines in RSR in the shelf seas of China, the Yellow Sea, and the East China Sea from 1997 to 2009. Compared with the RSR before 1997, no significant changes in mean RSR were found after 1997, except in the Bohai Sea. In addition, relative change in the RSR of echinoderms and species richness of macrobenthos led to more changes (decrease or increase) in their respective biomasses. Our results imply that changes in species richness may alter the macrobenthic productivity of the marine benthic ecosystem.

Spatial assessment of artisanal fisheries and their potential impact on the seabed: the Cap de Creus regional case study (northwestern Mediterranean Sea)

The northwestern Mediterranean region faces two contrasting realities: intensive fishing activity and a rising awareness among citizens of the need to protect ecologically important areas. In NE Spain, a large portion of the Cap de Creus area will be declared a Natura 2000 offshore site, establishing a large Marine Protected Area. This study examines the spatial distribution of artisanal fisheries and their potential impact on key vulnerable ecosystem components (KVECs) in the region. Data collection is based on a questionnaire-based survey in the absence of better records. An integrative map showing potential cumulative impact values for the Cap de Creus region was developed, including fishing gear pressure on selected KVECs. The most potentially impacted areas were found along the coast and on canyon margins. Results showed that different types of fishing gears converge, implying a higher impact on certain benthic communities and KVECs, with the greatest spatial coverage in coralligenous areas, Posidonia beds and maerl beds. When fishing log book and vessel monitoring system data are not available, the use of fishermen surveys linked to geographical information system tools can provide fundamental information for further implementation of effective measures for ecosystem-based management aimed at improving conservation of marine benthic ecosystems.

Is long-term ecological functioning stable: The case of the marine benthos?

It is widely acknowledged that human activities are contributing to substantial biodiversity loss and that this threatens ecological processes underpinning human exploitation of ‘ecosystem services’ (defined by the Millennium Ecosystem Assessment as ‘the benefits people obtain from ecosystems’). In the present study we consider three ‘intermediate ecosystem services’ in both contemporary and ancient marine systems and although ‘ecosystem services’ per se did not exist in the Jurassic our study seeks to consider the future provision of these services and so the term is retained. We consider the temporal patterns in benthic marine ecosystems: (1) spanning four decades at two offshore stations in the North Sea, UK and (2) over millennial scales in Late Jurassic UK palaeocommunities. Biological traits analysis is used to link changes in taxonomic composition to variations in ecological functioning and the potential supply of three ‘intermediate’ ecosystem services: the ability to provide food to fish and other predators, benthic nutrient regeneration and carbon cycling. We examine whether changes in taxonomic composition drive temporal variation in functioning, whether this variation increases over time and the extent to which species turnover is comparable in contemporary and ancient systems. Taxonomic variability was of a similar magnitude in all three systems and there was evidence for changes in functioning linked to changes in several (key or rivet) taxa. During other periods resilience maintained functioning in the face of taxonomic change. These results suggest that in these benthic systems the Biodiversity–Ecosystem Functioning relationship is idiosyncratic, but a degree of temporal stability in functioning is maintained such that the ecosystem services they underpin would also be stable during decadal and longer-term changes.

The necessity of DNA taxonomy to reveal cryptic diversity and spatial distribution of meiofauna, with a focus on Nemertea.

Meiofauna represent one of the most abundant and diverse communities in marine benthic ecosystems. However, an accurate assessment of diversity at the level of species has been and remains challenging for these microscopic organisms. Therefore, for many taxa, especially the soft body forms such as nemerteans, which often lack clear diagnostic morphological traits, DNA taxonomy is an effective means to assess species diversity. Morphological taxonomy of Nemertea is well documented as complicated by scarcity of unambiguous character states and compromised by diagnoses of a majority of species (and higher clades) being inadequate or based on ambiguous characters and character states. Therefore, recent studies have advocated for the primacy of molecular tools to solve the taxonomy of this group. DNA taxonomy uncovers possible hidden cryptic species, provides a coherent means to systematize taxa in definite clades, and also reveals possible biogeographic patterns. Here, we analyze diversity of nemertean species by considering the barcode region of the mitochondrial gene Cytochrome Oxidase subunit I (COI) and different species delineation approaches in order to infer evolutionarily significant units. In the aim to uncover actual diversity of meiofaunal nemerteans across different sites in Central America, COI sequences were obtained for specimens assigned here to the genera Cephalothrix, Ototyphlonemertes, and Tetrastemma-like worms, each commonly encountered in our sampling. Additional genetic, taxonomic, and geographic data of other specimens belonging to these genera were added from GenBank. Results are consistent across different DNA taxonomy approaches, and revealed (i) the presence of several hidden cryptic species and (ii) numerous potential misidentifications due to traditional taxonomy. (iii) We additionally test a possible biogeographic pattern of taxonomic units revealed by this study, and, except for a few cases, the putative species seem not to be widely distributed, in contrast to what traditional taxonomy would suggest for the recognized morphotypes.

Unraveling free-living marine nematode community structure from a biodiversity-rich tropical coastal setting based on molecular approaches

Free-living marine nematodes are ubiquitous in marine benthic ecosystems and play a key role in ecosystem processes. However limited information exists to date on free-living marine nematode community structure and diversity from biodiversity-rich tropical coastal environments. In this study, molecular tools based on the amplification, clone library generation and sequencing of the nematode 18S rRNA marker were employed to study free-living marine nematode community structure from two sites located in the Central West coast of India. Results based on the sequencing of 110 clones showed dominance of Enoplid and Chromadorid-like nematode 18S rRNA sequences, in addition to Monhysterid and Desmodorid-like sequences across study sites. Ptycholaimellus and Tripyloides-like nematode 18S rRNA sequences were abundant in clone libraries from the study sites. Based on morpho-taxonomic analysis, nineteen free-living marine nematode taxa were identified from both the study sites. Many of the identified taxa such as Ptycholaimellus sp., Tripyloides sp., and Terschellingia longicaudata were also detected in clone library sequences indicating that there was congruency between molecular and morphological approaches. At the same time, a sizeable number of sequences showed identity scores of only 87–96 % with published marine nematode 18S rRNA sequences available in databases indicating that the study sites harbour unreported species of marine nematodes. This finding was also supported by the presence of novel sub-clades based on phylogeny and OTU analysis where a sizeable number of singletons were detected. This study highlights the importance of including 18S rRNA marine nematode sequences in published nucleotide databases targeted specifically from biodiversity-rich tropical coastal regions so that it can ultimately improve our understanding of marine nematode community structure and diversity patterns, population genetics and nematode systematics.

Stable isotope ratios reveal food source of benthic fish and crustaceans along a gradient of trophic status in the East China Sea

The East China Sea (ECS) receives large quantities of particulate organic matter (POM) and inorganic nutrients transported from the Changjiang (Yangtze River), which have produced high productivity in the northwestern ECS. This study evaluated potential contributions of terrigenous POM (allochthonous food source) and nutrient-induced marine production (autochthonous source) to the ECS benthic ecosystem by analyzing stable isotopic compositions of phytoplankton, zooplankton, benthic crustaceans and fish. Benthic consumers exhibited δ13C values similar to those of their autochthonous food sources (i.e., phytoplankton and zooplankton), revealing their major reliance on marine production. In contrast, the δ13C values of benthic fish (−19.6‰ to −13.5‰) and crustaceans (−18.9‰ to −15.0‰) were much higher than that of terrigenous POM (−25.7‰), which generally accounted for less than 20% of the most fish diet. Phytoplankton and zooplankton generally exhibited higher δ13C values at eutrophic and highly productive inshore sites than at oligotrophic offshore sites. This enrichment of inshore δ13C values was mainly attributed to lower photosynthetic fractionation during algal blooms, an effect that was further enhanced during flood period of the Changjiang. The δ13C values of demersal fish assemblages were also significantly higher at inshore sites and decreased seaward. However, fish δ15N values and their estimated trophic levels showed relatively small spatial variation. The disproportionate variations in δ13C and δ15N values suggested that the enriched C isotopic signatures derived from an elevated δ13C baseline of the inshore food web instead of trophic enrichment of the isotopic ratios. The significantly positive correlations between concentrations of chlorophyll a and nutrients versus fish δ13C provided further evidence for the use of pelagic algal bloom materials by inshore consumers. The isotopic and oceanographic survey data suggested that inorganic nutrients discharged from the Changjiang River nourish benthic consumers in the ECS and play an important role in linking marine benthic ecosystems to local pelagic primary production as well as to the adjacent terrestrial watershed.

Interactive effects of hypoxia and PBDE on larval settlement of a marine benthic polychaete

Marine benthic polychaete Capitella sp. I is widely known to adapt to polluted habitats; however, its response to xenobiotics under hypoxic conditions has been rarely studied. This research aimed to test the hypothesis that interactive effects of hypoxia and congener BDE-47 of polybrominated diphenyl ethers (PBDE), which is ubiquitous in marine sediments, may alter the settlement of Capitella sp. I. Our results revealed that under hypoxic condition, settlement success and growth in body length of Capitella larvae were significantly reduced compared to those under normoxia of similar BDE-47 concentration. While no significant changes in morphology of settled larvae were noted in both exposure conditions, the presence of BDE-47 could enhance polychaete growth. The present findings demonstrated that the interactive effects of hypoxia and environmentally realistic concentrations of BDE-47 in sediments could affect polychaete settlement, which, in turn, reduce its recruitment and subsequent population size in the marine benthic ecosystem.

From the Arctic to the Antarctic: the major, minor, and trace elemental composition of echinoderm skeletons

AbstractBiogenic carbonate production in benthic marine ecosystems is dominated by representatives of the Echinodermata. Carbon and other major, minor, and trace elements are exported to the seabed where they accumulate or dissolve. Preserved carbonates (Mg‐calcite) have applications in oceanography and geochemistry and are used to reconstruct various parameters of ancient seawater, such as temperature (from Mg/Ca, Sr/Ca), seawater Mg/Ca (from Mg/Ca), and pH (from B/Ca). In general, the benthos is widely ignored for its role in the global carbon cycle despite the importance of echinoderms as a carbon sink (∼0.1–0.2 Pg C/yr). Echinoderms produce their skeletons from Mg‐calcite, which is more soluble than pure calcite and, therefore, more vulnerable to ocean acidification (OA). Minor and trace elements can also destabilize the calcite lattice, increasing the mineral's solubility. Little is known about the concentration of such elements in echinoderm tests. Expanding our knowledge on echinoderm skeleton composition will improve our understanding of elemental flux in the oceans. Furthermore, establishing relationships between the physical parameters of seawater and minor/trace elemental ratios within echinoderm Mg‐calcite should expand the utility of fossils as geochemical archives. Herein, we present elemental composition data for Asteroidea (n = 108; 9 families, 23 species), Echinoidea (n = 94; 8 families, 12 species), Ophiuroidea (n = 24; 4 families, 5 species), Holothuroidea (n = 7; 3 families, 3 species), and Crinoidea (n = 3; 1 family, 1 species), collected from the Arctic to the Antarctic oceans, from depths ranging from surface waters to 1200 m. The following elements were measured and normalized to [Ca]: Li, Be, Mg, Al, P, S, K, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Rb, Sr, Y, Zr, Mo, Ag, Cd, Sn, Sb, Te, Ba, La, Ce, Nd, Dy, W, Re, Au, Hg, Tl, Pb, Bi, and U. Data are presented for the whole body, arms (plates), calcareous ossicles, spines, and test plates. Elements were quantified using inductively coupled plasma mass spectrometry. Our study presents the most comprehensive data set to date for a phylum whose skeletons are composed of Mg‐calcite.

The Mediterranean Benthic Herbivores Show Diverse Responses to Extreme Storm Disturbances

Catastrophic storms have been observed to be one of the major elements in shaping the standing structure of marine benthic ecosystems. Yet, little is known about the effect of catastrophic storms on ecosystem processes. Specifically, herbivory is the main control mechanism of macrophyte communities in the Mediterranean, with two main key herbivores: the sea urchin Paracentrotus lividus and the fish Sarpa salpa. Consequently, the effects of extreme storm events on these two herbivores (at the population level and on their behaviour) may be critical for the functioning of the ecosystem. With the aim of filling this gap, we took advantage of two parallel studies that were conducted before, during and after an unexpected catastrophic storm event. Specifically, fish and sea urchin abundance were assessed before and after the storm in monitored fixed areas (one site for sea urchin assessment and 3 sites for fish visual transects). Additionally, we investigated the behavioural response to the disturbance of S. salpa fishes that had been tagged with acoustic transmitters. Given their low mobility, sea urchins were severely affected by the storm (ca. 50% losses) with higher losses in those patches with a higher density of sea urchins. This may be due to a limited availability of refuges within each patch. In contrast, fish abundance was not affected, as fish were able to move to protected areas (i.e. deeper) as a result of the high mobility of this species. Our results highlight that catastrophic storms differentially affect the two dominant macroherbivores of rocky macroalgal and seagrass systems due to differences in mobility and escaping strategies. This study emphasises that under catastrophic disturbances, the presence of different responses among the key herbivores of the system may be critical for the maintenance of the herbivory function.

Marine conservation planning in practice: lessons learned from the Gulf of California

ABSTRACTOverfishing, pollution, coastal development and climate change threaten marine biodiversity globally and compromise the services that marine ecosystems provide. Systematic conservation planning (SCP) provides a framework to identify areas where actions can be effective in addressing these threats, while minimizing the costs of interventions. This study investigated the application of SCP in the Gulf of California, a marine hotspot where seven prioritization exercises have been undertaken.The review of planning exercises showed that the use of SCP methods has progressed slowly (gaps include planning for land–sea connections and ecosystem services) and highlighted benefits and difficulties of applying SCP principles and tools.Despite some convergence, important spatial differences were found in priorities between plans. Convergence was evident in well‐studied shallow and benthic marine ecosystems. There were also important differences related to the planning approach, methods and extent. Divergence between methodological and spatial similarities between plans suggests that additional factors (e.g. manually delineating priority areas, incorporating updated datasets, random error), in addition to data and objectives, play an important role in defining the distribution of conservation priorities.According to expert opinion, the implementation of new marine protected areas (MPAs) in the region has been influenced by some of the planning exercises. However, uptake of planning outputs has progressed slowly for many reasons (e.g. conflicting mandates and interests between organizations, limited technical capacities and resources, insufficient political commitment). Other benefits of planning included: developing institutional skills and knowledge; improving collaboration and coordination between organizations (including agencies, and local, regional and national NGOs); converging on the need to assess priorities for marine conservation in regional context; and building trust among organizations.The existence of multiple marine conservation plans in the Gulf of California also highlighted some of the complexities and benefits of having multiple sets of priorities.Copyright © 2013 John Wiley & Sons, Ltd.