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1. 1. Exposure to hypoxic sea water (pO2 = 50mm Hg) and hyposalinity (20%.) caused the heart rate of Patella granularis to decline rapidly. This was particularly marked in hypoxia where normal heart rate (50 beats/min) fell initially to between 15–30 beats/min, and later (after 2 hr) cardiac arrest occurred. When oxygen tension and salinity were eventually normalized, heart rate became significantly elevated, above the normal rate. 2. 2. In Siphonaria capensis, exposure to reduced oxygen tension and salinity usually induced a regular, although often delayed (after 2 hr) bradycardia ( 3. 3. The significance of the different heart beat patterns by the limpet species, which may be linked with respiratory/metabolic responses, is discussed with regard to the respective capacities of the species for colonization of upper-shore pools.

International audience; During chick-rearing, albatrosses can alternate between long foraging trips that provide the main source of food for the adults and short foraging trips that they use to feed their young. This flexibility in foraging behaviour can lead to differences in diet composition between adults and chicks and implies that they may be vulnerable in different ways to food shortages. The trophic ecology of the Greyheaded albatross Thalassarche chrysostoma was investigated at the sub-Antarctic Prince Edward Islands during the chick-rearing period in April 2006 using a combination of approaches. Diets of adults and chicks were assessed using stable isotope ratios and fatty acid (FA) profiles of blood and/or stomach oils, in addition to stomach contents analysis. Fish from the family Macrouridae and cephalopods (particularly the onychoteuthid Kondakovia longimana) were the primary prey, whereas crustaceans (krill Euphausia superba) represented a smaller proportion of the stomach contents. Stomach oil FA profiles contained more monounsaturated FA than the profiles of plasma, which were richer in saturated FA and arachidonic acid (20:4n-6). There was also a distinct separation of adults from chicks, with higher levels of monounsaturates in chick plasma, and higher saturated FA levels (particularly 16:0) in the adult plasma. Stable carbon isotope ratios of whole blood were similar in adults and chicks, whereas stable nitrogen isotope ratios showed significant enrichment by [1% in chicks. The combined FA, stable isotopes and stomach contents analyses suggest clear differences in diet quality between adults and chicks, with chicks feeding at a higher trophic position through feeding more on highly nutritious fish and adults keeping much of the less nutritious zooplankton for themselves.

Reports on a major, multi-disciplinary cruise was organised to cover the full extent of the landward border of the northern Agulhas Current for the first time. This was done under the auspices of the African Coelacanth Ecosystem Programme as a South African contribution to the international Agulhas and Somali Current Large Marine Ecosystem.Reports on the cruise objectives, observations and some preliminary results.

The universal temperature-dependence model (UTD) of the metabolic theory of ecology (MTE) proposes that temperature controls mass-scaled, whole-animal resting metabolic rate according to the first principles of physics (Boltzmann kinetics). Controversy surrounds the model's implication of a mechanistic basis for metabolism that excludes the effects of adaptive regulation, and it is unclear how this would apply to organisms that live in fringe environments and typically show considerable metabolic adaptation. We explored thermal scaling of metabolism in a rocky-shore eulittoral-fringe snail ( Echinolittorina malaccana ) that experiences constrained energy gain and fluctuating high temperatures (between 25°C and approximately 50°C) during prolonged emersion (weeks). In contrast to the prediction of the UTD model, metabolic rate was often negatively related to temperature over a benign range (30–40°C), the relationship depending on (i) the temperature range, (ii) the degree of metabolic depression (related to the quiescent period), and (iii) whether snails were isolated within their shells. Apparent activation energies ( E ) varied between 0.05 and −0.43 eV, deviating excessively from the UTD's predicted range of between 0.6 and 0.7 eV. The lowering of metabolism when heated should improve energy conservation in a high-temperature environment and challenges both the theory's generality and its mechanistic basis.

1. 1. Aerial heart rate and O2 linearly correlated for Patella granularis and Siphonaria oculus when these parameters were varied by changing ambient temperature. This relationship for P. granularis was significantly transposed above that for S. oculus. 2. 2. While prolonged aerial exposure (+24hr) lowered the curve for heart rate against O2 for P. granularis below that determined over short-term exposure (< 12 hr), it had no significant effect on this relationship for S. oculus. 3. 3. The correlations of heart rate and oxygen consumption are discussed in terms of functioning of the circulatory system and the predictability of one parameter from the other.

When exposed to air, the phylogenetically distant intertidal limpets Patella granularis (Prosobranchia) and Siphonaria oculus (Pulmonata) displayed diferent levels of survival and metabolic adjustment. Siphonaria oculus lost water at a significantly higher rate, a response probably relating to its less domed shell Despite this, lethal exposure time and lethal water loss ($LT_{50} = 158 h$; $LD_{50} = 59\%$) were considerably higher than for P. granularis ($LT_{50} = 89 h$; $LD_{50} = 34\%$). Oxygen uptake rates (\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage{wasysym} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document}${\mathrm{\dot{V}_{O_{2}}}}$\end{document}) for both species remained constant over 12 h in air of 100% relative humidity (RH), when water loss was presumably negligible,...

During a combined hydroacoustic-trawling survey at the Prince Edward Arch~pelago, a kelp bed of Macrocystis laevis growing at a maximum depth of 68 m was repeatedly observed in the open shelf area This is the deepest population ever described for any species of giant kelp. Nutrient availability and temperature in the area were found to have no significant impact on kelp production and distribution. Likewise, measurements of photon flux density showed that neither plant growth nor sporophyte formation was likely to have been light-inhibited during the period of the observations. However, since irradiance levels in the deep kelp bed were close to the lower threshold for growth, the absence of plants below 68 m depth was probably determined by light availability. Around Marion Island, where M. laevis is found only within the 20 m isobath, the offshore limit of the kelp beds is controlled by availability of suitable rock substrata. The inshore limit appears to be set by the maximum height of storm-induced waves. Four species of Macrocystis are generally recognized: M, integrlfolia, M, angustifolja, M. pyrifera and the recently described M. laevis (Womersley 1954, Neushul 1971, Hay 1986, Brostoff 1988). Macrocystis kelps are found in cold temperate oceans with surface temperatures varying from 0 to 20 OC, and their main distribution is circumpolar in the Southern Hemisphere, between 40 and 60" S (Table 1; Cribb 1954, Michanek 1983). They are also present in the major coastal upwelling areas. On the west coast of South Africa they occur between 33"24' and 34"8'S and on the Pacific coast of South America extend almost to the equator, reappearing in North America along Baja California and reaching southern Alaska to the north (Table 1). Only 2 species of Macrocystis are represented in the Southern Ocean: M. pyrifera and M. laevis. While M. pyrifera is widely distributed from subantarctic South America to New Zealand, and occurs at most islands in the Atlantic and Indian sectors of the Southern Ocean, M. laevis is endemic to the Prince Edward Archipelago

Combined acoustic (12 and 120 kHz) and trawling (RMT-2 and Bongo net) surveys in offshore waters of the Prince Edward Archipelago revealed diurnal vertical migration of major prey species (the euphausiid Euphausia vallentini and the myctophid fish Krefftichthys andersson~) of landbased predators. Migration was from 200-400 m in the day to near-surface levels at night and was linked to feeding periodicity. Consistently high winds result in drift of surface waters (down to 10-20 m) and advection of prey over the shelf Within the seasonal limits of the investigation (autumn), an estimated 3200 t of zooplankton and 310 t of myctophid fish were carried over the shelf every 24 h. Predators in the archipelago consume ca 900 t of crustaceans and 1700 t of fish d' Thus, advection could supply sufficient crustaceans to the shelf area for the needs of the land-based predators, but is inadequate to support myctophid-feeding piscivores. Once over the shelf, prey attempting to migrate downwards ~vould be trapped by bottom topography and vulnerable to predation. The fit between estimates of advect~on and consumption of different prey types is supported by observed prey densities and predator behaviour Prey density in shelf and oceanic waters was similar at night, but decreased dramatically over, and downstream of, the shelf in the day. Rockhopper and Macaroni penguins are the most important crustacean predators and feed mainly over the shelf, with foraging ranges of about 30 and 100 km respectively. In contrast, King penguins account for >70 O/o of the fish consumed in the area and forage in deep waters, having an average foraging range of 300 km. This spatial segregation of the main predators is consistent with the availability of their prey.

Background Environmental heterogeneity plays a major role in invasion and coexistence dynamics. Habitat segregation between introduced species and their native competitors is usually described in terms of different physiological and behavioural abilities. However little attention has been paid to the effects of behaviour in habitat partitioning among invertebrates, partially because their behavioural repertoires, especially marine benthic taxa, are extremely limited. This study investigates the effect of gaping behaviour on habitat segregation of the two dominant mussel species living in South Africa, the invasive Mytilus galloprovincialis and the indigenous Perna perna. These two species show partial habitat segregation on the south coast of South Africa, the lower and upper areas of the mussel zone are dominated by P. perna and M. galloprovincialis respectively, with overlap in the middle zone. During emergence, intertidal mussels will either keep the valves closed, minimizing water loss and undergoing anaerobic metabolism, or will periodically open the valves maintaining a more efficient aerobic metabolism but increasing the risk of desiccation. Results Our results show that, when air exposed, the two species adopt clearly different behaviours. M. galloprovincialis keeps the shell valves closed, while P. perna periodically gapes. Gaping behaviour increased water loss in the indigenous species, and consequently the risk of desiccation. The indigenous species expressed significantly higher levels of stress protein (Hsp70) than M. galloprovincialis under field conditions and suffered significantly higher mortality rates when exposed to air in the laboratory. In general, no intra-specific differences were observed in relation to intertidal height. The absence of gaping minimises water loss but exposes the invasive species to other stresses, probably related to anoxic respiration. Conclusions Gaping affects tolerance to desiccation, thus influencing the vertical zonation of the two species. Valve closure exposes the invasive species to higher stress and associated energy demands, but it minimizes water loss, allowing this species to dominate the upper mussel zone, where the gaping indigenous P. perna cannot survive. Thus even very simple behaviour can influence the outcome of interactions between indigenous and invasive species.

Biotic stress may operate in concert with physical environmental conditions to limit or facilitate invasion processes while altering competitive interactions between invaders and native species. Here, we examine how endolithic parasitism of an invasive and an indigenous mussel species acts in synergy with abiotic conditions of the habitat. Our results show that the invasive Mytilus galloprovincialis is more infested than the native Perna perna and this difference is probably due to the greater thickness of the protective outer-layer of the shell of the indigenous species. Higher abrasion due to waves on the open coast could account for dissimilarities in degree of infestation between bays and the more wave-exposed open coast. Also micro-scale variations of light affected the level of endolithic parasitism, which was more intense at non-shaded sites. The higher levels of endolithic parasitism in Mytilus mirrored greater mortality rates attributed to parasitism in this species. Condition index, attachment strength and shell strength of both species were negatively affected by the parasites suggesting an energy trade-off between the need to repair the damaged shell and the other physiological parameters. We suggest that, because it has a lower attachment strength and a thinner shell, the invasiveness of M. galloprovincialis will be limited at sun and wave exposed locations where endolithic activity, shell scouring and risk of dislodgement are high. These results underline the crucial role of physical environment in regulating biotic stress, and how these physical-biological interactions may explain site-to-site variability of competitive balances between invasive and indigenous species. info:eu-repo/semantics/publishedVersion

The production and supply of larvae is enormously variable in the marine environment. This variation comes from multiple sources, some of which are understood whereas others remain enigmatic. The production of gametes can be enormously variable though is rarely systematically quantified. Fertilisation success (in species that broadcast spawn their gametes) is a major source of variation in the production of larvae and, because fertilisation is density dependent, non-intuitive relationships between population density and larval production may occur. By far the greatest challenge for understanding larval supply remains the role of mortality in the plankton—estimates are patchy and we still lack even a basic understanding of mortality rates for most species. The delivery of larvae to appropriate habitats is driven by a combination of hydrodynamics and larval behaviour, and the quality of larvae that arrive to these habitats can vary greatly. Overall, the high variability of larval dispersal and supply has fundamental consequences for both the evolution and ecology of marine benthic communities.

We investigated small-medium (1-300 km) scale variation in the foraging ecology of the African Black Oystercatcher during its breeding season, using traditional diet analysis coupled with carbon and nitrogen stable isotope analysis. Fieldwork was conducted between January and March 2006 and 2007, on rocky shores on the south-east coast of South Africa at East London, Kenton and Port Elizabeth. Middens of shelled prey left by adults feeding their chicks were collected from five territories and the abundances of the collected prey on the foraging areas were estimated using quadrats. Blood samples from 45 birds (16 females, 10 males and 19 chicks) and tissues from the predominant prey species on the territory of each breeding pair were collected for isotope analysis. The Manly-Chesson selectivity index revealed that adults feed their chicks preferentially with the limpet Scutellastra cochlear and the Mediterranean mussel Mytilus galloprovincialis, if available. A slight enrichment in the 15N stable-carbon isotope signature was observed towards the west in both prey and oystercatchers. Differences in isotope signatures between males and females from the same breeding pair indicate sex-related differences in the diet. Both had signatures indicating a mixed diet, but with males exhibiting a signature closer to that of limpets and females closer to that of mussels. In the single case where mussels were rare on the feeding territory, the two members of a pair showed carbon signatures which were identical and very similar to that of limpets. These results indicate dietary partitioning between genders in breeding pairs.

The relationships between three measurements of body size (carapace length, total body length and eye diameter) and three measurements of mass (wet, dry and ash-free dry weights) of the caridean shrimp Nauticaris marionis are presented. It is argued that a precisely defined carapace length is the most accurate indicator of body size. A conversion formula relating carapace length to total body length is also provided, as are conversion equations relating the different measures of mass.

The study of mussel settlement and recruitment requires the ability to identify the larvae of co-existing species. On the south coast of South Africa, an introduced (Mytilus galloprovincialis) and two indigenous (Choromytilus meridionalis and Perna perna) mussel species co-exist and compete for space. One of the indigenous species (P. perna) is invasive elsewhere. We provide discriminating features of their settlers based on post-larval shell morphology and hinge structure. Early post-larvae of P. perna can be identified by shell markings and shape. Small post-larvae of M. galloprovincialis and C. meridionalis are difficult to separate, but this can be done based on the proportions of the shell; larger post-larvae of M. galloprovincialis have diagnostic hair-like structures on the dissoconch. Detailed descriptions are provided that allow unambiguous identification of each species at sizes from 330 &#181m to 5 mm.Keywords: Choromytilus meridionalis, larval shell morphology, morphometrics, mussel settlement, Mytilus galloprovincialis, Perna pernaAfrican Journal of Marine Science 2008, 30(2): 233–240

Crabs of the family Hymenosomatidae are common in coastal and shelf regions throughout much of the southern hemisphere. One of the genera in the family, Hymenosoma, is represented in Africa and the South Pacific (Australia and New Zealand). This distribution can be explained either by vicariance (presence of the genus on the Gondwanan supercontinent and divergence following its break-up) or more recent transoceanic dispersal from one region to the other. We tested these hypotheses by reconstructing phylogenetic relationships among the seven presently-accepted species in the genus, as well as examining their placement among other hymenosomatid crabs, using sequence data from two nuclear markers (Adenine Nucleotide Transporter [ANT] exon 2 and 18S rDNA) and three mitochondrial markers (COI, 12S and 16S rDNA). The five southern African representatives of the genus were recovered as a monophyletic lineage, and another southern African species, Neorhynchoplax bovis, was identified as their sister taxon. The two species of Hymenosoma from the South Pacific neither clustered with their African congeners, nor with each other, and should therefore both be placed into different genera. Molecular dating supports a post-Gondwanan origin of the Hymenosomatidae. While long-distance dispersal cannot be ruled out to explain the presence of the family Hymenosomatidae on the former Gondwanan land-masses and beyond, the evolutionary history of the African species of Hymenosoma indicates that a third means of speciation may be important in this group: gradual along-coast dispersal from tropical towards temperate regions, with range expansions into formerly inhospitable habitat during warm climatic phases, followed by adaptation and speciation during subsequent cooler phases.

Variabilities in the responses of several South African red and green macroalgae to direct grazing and the responses of one green alga to cues from grazers were tested. We used two feeding experiments: (1) testing the induced responses of three red and one green algae to direct grazing by mesograzers and (2) a multi-treatment experiment, in which the direct and indirect effects of one macrograzer species on the green alga Codium platylobium were assessed. Consumption rates were assessed in feeding assays with intact algal pieces and with agar pellets containing non-polar extracts of the test algae. Defensive responses were induced for intact pieces of Galaxaura diessingiana, but were not induced in pellets, suggesting either morphological defence or chemical defence using polar compounds other than polyphenols. In contrast, exposure to grazing stimulated consumption of Gracilaria capensis and Hypnea spicifera by another grazing species. In the multi-treatment experiment, waterborne cues from both grazing and non-grazing snails induced defensive algal traits in C. platylobium. We suggest that inducible defences among macroalgae are not restricted to brown algae, but that both the responses of algae to grazers and of grazers to the defences of macroalgae are intrinsically variable and complex.

International audience; The southern coasts of Africa are influenced by two major oceanic currents, leading to biogeographic patterns in inshore and offshore species assemblages, and in the stable isotope signatures of suspended particulate matter and filter-feeding mussels. We used the stable isotope ratios of carbon (13C/12C) and nitrogen (15N/14N) from the blood and feathers of adult and chick Cape gannets (Morus capensis) to investigate whether the geographic differences observed at the lower levels in the marine communities are deep penetrating effects that reach top predators. Additionally, we evaluated whether trophic segregation occurs between adult and reared chick gannets, and whether a shift to wintering habitat occurs in adults. The study was conducted during the 2006 breeding season on Bird Island in the Agulhas system, and on Malgas and Ichaboe Islands, in the south and north Benguela respectively. Our results showed significant differences in the isotope ratios of members of different colonies, but no intra-colony differences between tissues or age groups. These results indicate that there is neither age-related nor temporal segregation in the diet of members of the same colony. Feather isotopic values suggest that adults remain all year round in the same habitats, and do not undertake long migration after reproduction. Since all gannets tend to target similar prey, we attributed among-colony differences in isotope signatures mostly to the oceanic conditions experienced by the main prey of birds rather than substantial differences in diet composition. Overall, isotopic signatures segregate the two current systems, with depleted carbon values in the Agulhas and enriched nitrogen values in the upwelled waters of the Benguela. Within the Benguela birds from Ichaboe in the north had higher δ15N values than those from Malgas in the south, which we attributed to differences in the functioning of the upwelling cells in the vicinity of the two colonies. Finally, slight variation in the proportion of main prey and discards from fisheries may contribute to the variation in the stable-isotope signatures between colonies in the Benguela.

BACKGROUND:The southern African tick shell, Nassarius kraussianus (Dunker, 1846), has been identified as being the earliest known ornamental object used by human beings. Shell beads dated from approximately 75,000 years ago (Pleistocene era) were found in a cave located on South Africa's south coast. Beads made from N. kraussianus shells have also been found in deposits in this region dating from the beginning of the Holocene era (

Invasive species can affect the function and structure of natural ecological communities, hence understanding and predicting their potential for spreading is a major ecological challenge. Once established in a new region, the spread of invasive species is largely controlled by their dispersal capacity, local environmental conditions and species interactions. The mussel Mytilus galloprovincialis is native to the Mediterranean and is the most successful marine invader in southern Africa. Its distribution there has expanded rapidly and extensively since the 1970s, however, over the last decade its spread has ceased. In this study, we coupled broad scale field surveys, Ecological Niche Modelling (ENM) and Lagrangian Particle Simulations (LPS) to assess the current invaded distribution of M. galloprovincialis in southern Africa and to evaluate what prevents further spread of this species. Results showed that all environmentally suitable habitats in southern Africa have been occupied by the species. This includes rocky shores between Rocky Point in Namibia and East London in South Africa (approx. 2800 km) and these limits coincide with the steep transitions between cool-temperate and subtropical-warmer climates, on both west and southeast African coasts. On the west coast, simulations of drifting larvae almost entirely followed the northward and offshore direction of the Benguela current, creating a clear dispersal barrier by advecting larvae away from the coast. On the southeast coast, nearshore currents give larvae the potential to move eastwards, against the prevalent Agulhas current and beyond the present distributional limit, however environmental conditions prevent the establishment of the species. The transition between the cooler and warmer water regimes is therefore the main factor limiting the northern spread on the southeast coast; however, biotic interactions with native fauna may also play an important role. Portuguese National Science Foundation (FCT) [EXCL/AAG-GLO/0661/2012, EXPL/BIA-BIC/1471/2012, CCMAR/BPD/0045/2013]; South African Research Chairs Initiative of the Department of Science and Technology; National Research Foundation

South Africa has a long track record in Southern Ocean and Antarctic research and has recently invested considerable funds in acquiring new infrastructure for ongoing support of this research. This infrastructure includes a new base at Marion Island and a purpose-built ice capable research vessel, which greatly expand research opportunities. Despite this investment, South Africa’s standing as a participant in this critical field is threatened by confusion, lack of funding, lack of consultation and lack of transparency. The research endeavour is presently bedevilled by political manoeuvring among groups with divergent interests that too often have little to do with science, while past and present contributors of research are excluded from discussions that aim to formulate research strategy. This state of affairs is detrimental to the country’s aims of developing a leadership role in climate change and Antarctic research and squanders both financial and human capital.

Organisms with different life-histories and abilities to disperse often utilise habitat patches in different ways. We investigated the influence of the size of patches of rock (separated by stretches of sand) on the density of pulmonate limpets (Siphonaria spp.) along 1500 km of the linear landscape of the South African coastline. We compared the influence of patch-size on two congeneric species with different modes of development, S. serrata a direct developer, and S. concinna a planktonic developer. We tested the spatial and temporal consistency of the effects of patch-size by sampling 7 independent regions spanning the distributional range of both species of limpets, and by sampling one region at monthly intervals for 1 year. Within each region or month, 4 small patches (60 m in length) were sampled. Across the entire geographic range and throughout the year, there were more of both species of limpets in large patches than in small patches. In most regions, there was greater variability in large patches than small patches. Variability within patches in a single region was similar throughout the year, with greater variability of both species in large than in small patches. We found little influence of the mode of development on the response of limpets to patch-size. Our findings highlight the importance of understanding patterns of distribution of species with respect to habitat heterogeneity in linear landscapes, and contradict the idea that organism mobility at an early ontogenetic stage directly affects habitat use.

The surface distribution of netphytoplankton (>20 μm) in the Atlantic sector of the Southern Ocean was investigated along two transects during early and late austral summer 1990/91. Sampling was under-taken at intervals of 60′ of latitude between 34° and 70°S for the analysis of nutrients and for the identification and enumeration of netphytoplankton. Peaks in total diatom abundances were recorded at the Antarctic Polar Front (APF), in the vicinity of the South Sand wich Islands, in the marginal ice zone and in the neritic waters of the Atlantic sector of Antarctica. Cluster analysis indicates the existence of two major zones between Southern Africa and Antarctica. Diatom abundance increased south of the Antarctic Polar From along both transects, which can be partially explained by gradients of silicate concentration. Small chain-forming species (e.g. Fragilariopsis kerguelensis and Nitzschia lineata) dominated the diatom assemblages in early summer, while larger species, such as Rhizosolenia hebetata f. semispina and Corethron criophilum, dominated late summer diatom assemblages. The predominance of typically ice-associated forms in early summer suggests that the release of epontic cells during ice melt provides the initial inoculum for the netphytoplankton biomass. These small diatoms are subsequently replaced by larger species.

This study forms part of a larger project in which five planimetric parameters have been used to study changes in the digestive epithelium of Littorina littorea under different environmental and physiological conditions. Our aim was to examine the effect of the reproductive cycle on these parameters in order to assess their usefulness as indicators of stress. A one way anova shows that the absolute parameters of mean epithelial thickness (MET), mean diverticulum radius (MDR) and mean luminal radius (MLR) vary significantly depending on the time of the year. This variation is highly correlated to the amount of digestive tissue present and hence negatively correlated to the reproductive state because gonad and digestive tissue volume are inversely related. Consequently, these parameters are not good indicators of stress. However, whereas the absolute size of the digestive acinus varies with the reproductive state of the animal, the MET, MDR and MLR retain the same proportions and therefore the ratios MET/MDR and MLR/MET remain constant. This makes them useful indicators of stress because they are independent of intrinsic variables such as the reproductive cycle.

The structure of rocky intertidal communities may be influenced by large-scale patterns of productivity. In this study we examine the in situ rates of production by intertidal epilithic microalgae (chlorophyll a production per unit area per month), intertidal nutrient concentrations (nitrates, nitrites, phosphates and silicates), and standing stocks of different functional-form groups of macroalgae around the South African coast, and their relationships to consumer biomass. Clear gradients of in situ intertidal primary production and nutrient concentrations were recorded around the South African coast, values being highest on the west coast, intermediate on the south and lowest on the east coast. Primary production by intertidal epilithic microalgae was correlated with nutrient availability and could also be related to nearshore phytoplankton production. The dominance patterns of different functional forms of macroalgae changed around the coast, with foliose algae prevalent on the west coast and coralline algae on the east coast. However, overall macroalgal standing stocks did not reflect the productivity gradient, being equally high on the east and west coasts, and low in the south. Positive relationships existed between the average biomass of intertidal intertebrate consumers (grazers and filter-feeders) and intertidal productivity, although only the grazers were directly "connected" to in situ production by epilithic intertidal microalgae. The maximum body size of a widely distributed limpet, Patella granularis, was also positively correlated with level of in situ primary production. The maximal values of biomass attained by intertidal filter-feeders were not related to intertidal primary production, and were relatively constant around the coast. At a local scale, filter-feeder biomass is known to be strongly influenced by wave action. This implies that the local-scale water movements over-ride any effects that large-scale gradients of primary production may have on filter-feeders. The large-scale gradient in intertidal productivity around the coast is thus strongly linked with grazer biomass and individual body size, but any effect it has on filter-feeder biomass seems subsidiary to the local effects of wave action.

Teske et al..-- 13 pages, 1 figure, 4 tables, additional material in https://doi.org/10.1186/1471-2148-11-176 Background Ecosystem engineers facilitate habitat formation and enhance biodiversity, but when they become invasive, they present a critical threat to native communities because they can drastically alter the receiving habitat. Management of such species thus needs to be a priority, but the poorly resolved taxonomy of many ecosystem engineers represents a major obstacle to correctly identifying them as being either native or introduced. We address this dilemma by studying the sea squirt Pyura stolonifera, an important ecosystem engineer that dominates coastal communities particularly in the southern hemisphere. Using DNA sequence data from four independently evolving loci, we aimed to determine levels of cryptic diversity, the invasive or native status of each regional population, and the most appropriate sampling design for identifying the geographic ranges of each evolutionary unit. Results Extensive sampling in Africa, Australasia and South America revealed the existence of "nested" levels of cryptic diversity, in which at least five distinct species can be further subdivided into smaller-scale genetic lineages. The ranges of several evolutionary units are limited by well-documented biogeographic disjunctions. Evidence for both cryptic native diversity and the existence of invasive populations allows us to considerably refine our view of the native versus introduced status of the evolutionary units within Pyura stolonifera in the different coastal communities they dominate. Conclusions This study illustrates the degree of taxonomic complexity that can exist within widespread species for which there is little taxonomic expertise, and it highlights the challenges involved in distinguishing between indigenous and introduced populations. The fact that multiple genetic lineages can be native to a single geographic region indicates that it is imperative to obtain samples from as many different habitat types and biotic zones as possible when attempting to identify the source region of a putative invader. "Nested" cryptic diversity, and the difficulties in correctly identifying invasive species that arise from it, represent a major challenge for managing biodiversity PR Teske was supported by a postdoctoral research fellowship for overseas study by the National Research Foundation, an overseas study grant from the Ernest Oppenheimer Memorial Trust and a Rhodes University postdoctoral research fellowship. M Rius was supported by the 'Agencia Española de Cooperación Internacional para el Desarrollo' from the Spanish 'Ministerio de Asuntos Exteriores y de Cooperación'. The work was partially funded by a grant from the DST-NRF Centre of Excellence for Invasion Biology (to M Rius), by the South African Research Chairs Initiative of the Department of Science and Technology and the National Research Foundation (to CD McQuaid), by grants from Macquarie University (MQ A006162) and the Australian Research Council (DP110101275) to LB Beheregaray, and by Flinders University. This contribution represents manuscript no. 40 of the Molecular Ecology Group for Marine Research (MEGMAR)

A high resolution study of chlorophyll a and primary production distribution was carried out in the Atlantic sector of the Southern Ocean during the austral summer of 1990–91. Primary production (14C assimilation) and photosynthetic capacity levels at frontal systems were among the highest recorded during the cruise (2.8–6.3 mgC·m−3·h−1, and 1.3–4.7mgC·mgChl a−1·h−1, respectively). Blooms at ocean fronts were strongly dominated by specific size classes and species. This suggests that the increase in biomass was probably the result of an enhancement of in situ production by selected components of the phytoplankton assemblage, rather than accumulation of cells through hydrographic forces. This hypothesis is supported by the high variability of photosynthetic capacities at adjacent stations along the transects. Blooms (ca 2.7–3.5 mg Chl a·m−3) were found at three oceanic fronts (the Subtropical, Subantarctic and Antarctic Polar Fronts) during the early summer. These were equivalent to, or denser than, blooms in the Marginal Ice Zone and at the Continental Water Boundary. Seasonal effects on phytoplankton community structure were very marked. In early summer (December), netphyto-plankton (>20 μm) was consistently the major component of the frontal blooms, with the chain-forming diatoms Chaetoceros spp. and Nitzschia spp. dominating at the Subantarctic and Antarctic Polar Fronts, respectively. During late summer (February), nanophytoplankton (1–20 μm) usually dominated algal communities at the main frontal areas. Only at the Antarctic Polar Front did netphytoplankton dominate, with the diatom component consisting almost exclusively of Corethron criophilum. An early to late summer shift of maximum phytoplankton biomass from north to south of the Antarctic Polar Front was observed. Spatial covariance between silicate levels and water-column stability appeared to be the main factor controlling phytoplankton production at the Antarctic Polar Front. Low silicate concentrations may have limited diatom growth at the northern edge of the front, while a deep mixed layer depth reduced production at the southern edge of the front.

Mutualistic relations between plants and animals are well documented on land but have received less attention in marine systems. This study examined the relationship between the territorial intertidal limpet Patella longicosta and the crustose brown alga Ralfsia verrucosa. Adult Patella are found exclusively in association with Ralfsia, on which they feed, while Ralfsia occurs primarily, but not exclusively, in Patella territories. Ralfsia benefits directly from both the presence and the territorial behaviour of Patella. Algal productivity was assessed by measuring oxygen evolution and utilization in situ and deriving photosynthesis/irradiance curves. Productivity was increased by about 30% by the presence of Patella in both summer (P max of grazed algae 0.0098; ungrazed algae 0.0063 mg C · cm-2 · h-1) and winter (P max grazed algae 0.0081; ungrazed algae 0.0053 mg-2 · C · h-1). Algal growth rates were not significantly increased by the application of limpet mucus in the laboratory. We did not examine nutrient regeneration by the limpet, but the increase in photosynthetic rate may depend on the limpet's grazing pattern which creates secondary sites for growth. Ralfsia also benefited from the territorial behaviour of Patella. The effects of different grazing regimes were investigated in different seasons by removing territorial limpets and either excluding all limpets using copper-based antifouling paint, or allowing access to non-territorial limpets (mostly P. oculus) using partial paint barriers. Exclusion of all limpets resulted in rapid overgrowth of Ralfsia plants by the foliose green alga Ulva sp.. Where non-territorial limpets had access to the plants overgrowth was reduced but Ralfsia plants were entirely removed by destructive grazing. Non-territorial grazers removed 90% of Ralfsia plants within 4 weeks in summer and 60% in winter. In control treatments P. longicosta prevented overgrowth by Ulva and actively excluded vagrant grazers, preventing overgrazing. Based on these findings, the association between the limpet and alga can be regarded as a nonobligate mutualism.

There is considerable interest in understanding how ectothermic animals may physiologically and behaviourally buffer the effects of climate warming. Much less consideration is being given to how organisms might adapt to non- climatic heat sources in ways that could confound predictions for responses of species and communities to climate warming. Although adaptation to non-climatic heat sources (solar and geothermal) seems likely in some marine species, climate warming predictions for marine ectotherms are largely based on adaptation to climatically relevant heat sources (air or surface sea water temperature). Here, we show that non-climatic solar heating underlies thermal resistance adaptation in a rocky-eulittoralfringe snail. Comparisons of the maximum temperatures of the air, the snail's body and the rock substratum with solar irradiance and physiological performance show that the highest body temperature is primarily controlled by solar heating and re-radiation, and that the snail's upper lethal temperature exceeds the highest climatically relevant regional air temperature by approximately 22°C. Non-climatic thermal adaptation probably features widely among marine and terrestrial ectotherms and because it could enable species to tolerate climatic rises in air temperature, it deserves more consideration in general and for inclusion into climate warming models. © 2010 The Royal Society., link_to_OA_fulltext

The recently described species Macrocystis laevis Hay is endemic to the Prince Edward Islands. Aerial photographs of Marion Island were used to outline the distribution of the kelp and to assess its cover. M. laevis occurs along the lee shore of the island, between the 5 and 20 m isobaths. Plant densities and gross plant morphology were measured by divers during April/May 1988. Net production was estimated from growth measurements taken in April/May 1988 and 1989 and again during August 1989. The mean biomass of kelp was 0.67 kgC·m−2 within the kelp beds. Net production was estimated at 7.7 gC·m−2·d−1 and 11.5 gC·m−2d−1 during the months of April and August respectively. M. laevis had a uniform frond-length frequency distribution, which suggests that only the oldest fronds are lost by wave action or senescence. Based on calculations for M. laevis and Durvillaea antarctica (the two species making up most of the macrophyte biomass) macrophytes are more productive per unit area than the phytoplankton but contribute less to the seas around the Prince Edward Islands by virtue of their small spatial coverage. Neither of the kelps lose much material as particulate or dissolved organic carbon through fragmentation. The extent of grazing on live M. laevis fronds is unknown, and only D. antarctica contributes to a macrofaunal detrital community. The contribution of M. laevis production to the nearshore ecology of the islands seems limited, as we suspect that almost all of its production is exported to the open ocean pelagic system.

Terrestrial and freshwater pulmonate snails exhibit a marked depression of aerobic metabolism during estivation. This is an adaptation for existence in periodically harsh environments and, though marine gastropods may undergo anaerobic metabolism, they have not been shown to adaptively depress aerobic metabolic rate. We compared the metabolic response to progressive aerial exposure of two intertidal gastropod limpets, a prosobranch and a pulmonate. The prosobranch Patella granularis maintained a constant heart rate until shortly before death. In contrast, the pulmonate Siphonaria oculus underwent facultative depression of heart rate, accompanied by a decline in oxygen consumption. Both heart rate and oxygen consumption returned to normal levels on reimmersion in water. Metabolic rate depression is energy conserving, and may account for the ability of S. oculus to extend higher up the shore than P. granularis, into areas where food availability is low. S. oculus is a primitive, marine pulmonate, periodically subject to harsh conditions, and its capacity for metabolic rate depression may represent a pre-adaptation for life on land.

Many rocky shores are subject to periodic inundation by sand, which is often thought to reduce species richness by eliminating organisms intolerant of sand scour or sand smothering. However, regular disturbance (e.g. inundation) should promote richness by preventing the development of low diversity climax communities. A study of faunal richness on 10 regularly inundated shores showed that inundation does promote richness, but by increasing habitat heterogeneity. Some species are excluded from parts of the shore by sand, but because of the patchiness of sand deposits they are rarely excluded from the entire shore. Other species are found only on rocks associated with sand, while typically sandy shore animals occur in the sand deposits themselves. Total richness (281 species) was greater than for local noninundated shores and sandy beaches combined.

The feeding dynamics of males and females of the sequential protandric shrimp Nauticaris marionis were investigated in late austral summer (April) 2002. Results of gut content analysis indicated that N. marionis is an opportunistic feeder preying on a variety of prey, with a preference for detritus, benthic amphipods and gastropods. Overall, pelagic prey made only an insignificant contribution to diet, and was only taken by males. Females of N. marionis exhibited cannibalism, particularly in incubation containers. There was no diel pattern in the feeding activity of N. marionis. In-situ daily rations of males (carapace length 7 mm) were equivalent to ≈10% and ≈5% of body dry weight, respectively.

Littorina africana knysnaensis (Philippi) exhibits a size gradient of increasing shell length up the shore on the Cape Peninsula caused by separate size dependent effects on juveniles and adults. There is no apparent correlation between mean shell length and density, and animals of separate size classes which are transferred to zones where they do not normally occur rapidly migrate to their original zones. Juvenile settlement occurs almost exclusively on the upper shore to avoid the heavy wave action of the lower Littorina zone. If tethered in the lower zones juveniles show a loss of body weight or may even be torn free of their tethers and lost. Juveniles do, however, occur in the lower zones where shelter from the effects of wave action is available in the form of narrow crevices. Adult animals have a much greater tenacity and when tethered, they develop a lower length/body weight ratio in the lower Littorina zone than in the upper where microphytic productivity decreases considerably. The greater tenacity of adults allows a gradual downshore migration of growing animals in response to gradients of food availability. The resulting size gradient of L.a. knysnaensis is the reverse of that predicted for such a supralittoral fringe species.

SUMMARY The physical and chemical properties of the waters of the Bot River estuary have been examined over a period of five years. The parameters measured were: electrical conductivity, pH, alkalinity, temperature, dissolved oxygen, total dissolved salts, sodium, magnesium, calcium, potassium, fluoride, chloride, nitrate, ammonia, sulphate, phosphate and silicate. The physical and chemical properties are mostly affected by artificial openings of and water-levels in the estuary.

On compare la structure trophique de biocenones intertidales de zones exposees et de zones non exposees a l'action des vagues (Cap de Bonne Esperance). L'exposition aux vagues agit a la fois sur la repartition verticale de la biomasse et la structure trophique de la biomasse totale. Les organismes filtrants, les carnivores et les omnivores presentent une biomasse nettement plus elevee dans la zone exposee. L'on suggere que la domination des zones exposees par les organismes filtrants sessiles et des cotes abritees par les algues et les herbivores mobiles expliquerait les vues divergentes, dans la bibliographie, sur l'importance relative de la competition et de la predation dans la structure des biocenoses de cotes rocheuses

Littorina africana knysnaensis (Philippi) increased markedly in mean shell length up the shore with preferential settlement in the higher zones. Density was greatest at the top of the shore (around 348 animals · m−2) but there was no apparent relationship between mean size or biomass · m−2 and density. Reproduction appears to involve pelagic larvae and recruitment is continuous throughout the year. Settlement success, however, was extremely variable and was probably influenced by offshore conditions. The total population declined slowly from November 1976 to March 1977 due to low rates of settlement and high mortality. From May 1977 to January 1978 recruitment rates were higher and mortality decreased resulting in a 231% rise in population over 8 months. Peak periods of settlement were in winter (May–June) and Summer (December–January). Juvenile cohorts appear at 2–3 mm and attain sexual maturity at ≈5 mm, growing to 6–7 mm in their first year. Maximum size of ≈ 10 mm is attained after 3 yr. Growth for animals in all zones was minimal in winter. Growth was maximal in spring for large animals (lowest zone), in early summer for medium animals (middle zone) and in late summer for small animals (top zone). This pattern in growth is thought to reflect the seasonal variability of the microphytic standing crop in the different zones.

Nucella dubia (Kr.) occurs in the middle and upper balanoid zone of rocky shores in the Cape of Good Hope. Ten prey species, all cirripedes or molluscs, were recorded under field conditions, diet being partially size dependent. Gastropods and barnacles were usually attacked through the opercular opening and rarely drilled. At Dalebrook the main prey were Tetraclita serrata Darwin in the mid-balanoid zone and Littorina africana knysnaensis (Phillipi) on the upper shore. Predator-prey relationships and the impact of predation contrasted strongly for these two prey species. Predation in the Littorina zone was cyclical. Nucella dubia migrated upshore from the upper balanoid as spring tides approached and downshore during neap tides. Both the number of whelks present and the percentage of them feeding peaked 1–2 days before spring tides. Whelk and Littorina size were positively correlated in predator-prey couples. Despite high rates of consumption (mean of 0.47 Littorina · whelk −1 ·day −1 over a 2-wk cycle) only ≈12% of the Littorina population are lost to predation per year. Caging experiments in the balanoid zone revealed consistently low predation rates (0.02 barnacles ·whelk −1 ·day −1 ) for both large and small whelks. Due to high whelk density (86·m −2 ) potential predation was estimated at 45.66% of the barnacle standing crop per year. This may be adequate to control barnacle density and maintain free space in barnacle beds. This study thus indicates that predation by Nucella dubia on sessile prey such as Tetraclita is greater than on the mobile Littorina and supports the suggestion of others that predators have a greater influence on sessile than mobile intertidal invertebrates.

Summary Field observations of the feeding behaviour of the slatey egret (Egretta vinaceigula) were carried out at Moremi in Botswana. A range of feeding activities previously unrecorded for the species were observed and an average activity index derived. Feeding activity was found to reach a peak around 14.30 h on each of 3 days of observation. The feeding strategy adopted varied at different times of the day as prey behaviour changed. Feeding was almost entirely on small fish and involved several forms of foot activities. In particular the percentage of feeding time spent foot stirring appears to correlate well with feeding success. Resume Le comportement d'alimentation de l'aigrette Egretta vinaceigula fut observe dans la region de Moremi au Botswana. Une suite d'activites, liees a la prise de nourriture et jusqu'a present non-documentees, fut etablie ainsi qu'un index d'activite moyenne. Au cours d'une periode d'observation de 3 jours, l'activite d'alimentation fut maximale vers 14 heures 30 chaque jour. Le mode d'alimentation variat au cours de la journee en function du comportement de la proie. La prise de nourriture se limitat presque entierement a de petits poissons, et fut accompagnee de plusieures formes d'agitation de la patte. En particulier, il y avait une correlation evidente entre d'une part, le pourcentage de la periode de prise de nourriture qui fut consacre aux agitations des pattes et d'autre part, le succes des tentatives de prise de nourriture.

Etude menee au Cap de Bonne Esperance a l'aide de l'analyse de grappe des donnees, pour 310 especes, sur 12 cotes rocheuses

Nitrogen uptake by the kelp Ecklonia maxima Osbeck and phytoplankton was examined under different conditions of nutrient availability in a kelp bed off the Cape of Good Hope by measuring nutrient depletion in large plastic bags by the kelp and 15N uptake by phytoplankton. E. maxima took up nitrate and ammonia, but not urea, and showed only a weak preference for reduced nitrogen. Phytoplankton absorbed all three forms of nitrogen available, with a preference for ammonia and urea. Ambient nitrate concentration exhibited a marked and rapid decrease with northerly winds and an increase in response to offshore southerly winds. Nitrogen uptake by E. maxima was linearly related to ambient concentration and did not saturate even at nitrate concentrations >20μg-at N l-1, resulting in a significantly higher tissue nitrogen content under upwelling conditions. Nitrate imported by upwelling was the chief source of nitrogen utilised within the kelp bed. Locally regenerated nitrogen (ammonia and urea) was calculated to contribute only ca 4% of total nitrogen uptake during upwelling and 30% during the relaxation or downwelling phase.

Two closely located islands on the west coast of South Africa support widely different benthic communities. The biota at Malgas Island is dominated by seaweeds and by rock lobsters that consume settling mussels, thereby preventing the establishment of the mussels. They also prey on whelks, although one speces, Burnupena papyracea, is protected from predation by a commensal bryozoan that covers its shell. Marcus Island has extensive mussel beds, but rock lobsters and seaweeds are virtually absent; whelks (mostly Burnupena spp.) occur at high densities. Rock lobsters transferred to Marcus Island were overwhelmed and consumed by the whelks, reversing the normal predatorprey relation between the two species. These two contrasting communities persisted during 4 years and may represent multiple states of the same ecosystem. This effective change of roles between a prey species and its chief predator may provide an intrinsic mechanism to maintain these states following the initial exclusion of the predator.