Macroalgae contribute to the diet of Patella vulgata from contrasting conditions of latitude and wave exposure in the UK

Analysis of gut contents and stable isotope composition of intertidal limpets (Patella vulgata) showed a major contribution of macroalgae to their diet, along with microalgae and invertebrates. Specimens were collected in areas with limited access to attached macroalgae, suggesting a major dietary component of drift algae. Gut contents of 480 animals from 2 moderately wave exposed and 2 sheltered rocky shores in each of 2 regions: western Scotland (55–56°N) and southwest England (50°N), were analysed in 2 years (n = 30 per site per year). The abundance of microalgae, macroalgae and invertebrates within the guts was quantified using categorical abundance scales. Gut content composition was compared among regions and wave exposure conditions, showing that the diet of P. vulgata changes with both wave exposure and latitude. Microalgae were most abundant in limpet gut contents in animals from southwest sites, whilst leathery/corticated macroalgae were more prevalent and abundant in limpets from sheltered and northern sites. P. vulgata appears to have a more flexible diet than previously appreciated and these keystone grazers consume not only microalgae, but also large quantities of macroalgae and small invertebrates. To date, limpet grazing studies have focussed on their role in controlling recruitment of macroalgae by feeding on microscopic propagules and germlings. Consumption of adult algae suggests P. vulgata may also directly control the biomass of attached macroalgae on the shore, whilst consumption of drift algae indicates the species may play important roles in coupling subtidal and intertidal production

The influence of mussel-modified habitat on Fucus serratus L. a rocky intertidal canopy-forming macroalga

The influence of habitat modification by Mytilus edulis L. on the settlement and development of Fucus serratus populations was investigated on rocky shores of the Isle of Anglesey, North Wales. Settlement of fucoids was higher inside mussel habitat than outside on one of two shores studied. The effect of microhabitat on survival of fucoid germlings was examined by transplanting the germlings into and outside mussel habitats, each with and without the exclusion of grazers. Observation showed that periwinkles and top shells were abundant in mussel habitat, while limpets dominated bare rock. Exclusion of grazers greatly enhanced the survival of fucoid germlings in both habitats, indicating that while mussel habitat supports a different grazer assemblage to bare rock, both assemblages are important in limiting fucoid recruitment. The risk of dislodgement was assessed and compared between fucoids growing on mussel shells and bare rock. In situ pull-tests showed that less force was required to detach large fertile thalli growing on mussel shells than those growing on the rock. Adhesion was generally broken between the mussel and the rock rather than between the holdfast and the mussel. These observations indicate that mussels provide an unstable substrate for mature fucoids. Overall results suggest that a negative effect of mussel-modified habitat on fucoids is profound in adults; but the effect is context-dependent in juveniles and can be positive at settlement. Results from a survey on population structure of fucoids across two shores showed that there were greater numbers of large fertile fucoids growing directly attached to rock than on mussel shells, while there was no difference for juvenile fucoids confirming the experimental results. Moreover thalli larger than 60 cm were found only on the rock but not on shells. This finding suggests that a mussel dominated habitat may have a significant impact on reproductive output in fucoid populations

No Detectable Broad-Scale Effect of Livestock Grazing on Soil Blue-Carbon Stock in Salt Marshes

Grassland carbon capturing and storage (CCS) is thought to benefit from regulation of grazing. The impact is likely to depend on livestock density. Yet, few studies have tested this principle or evaluated the consistency of grazer-carbon relationships across multiple sites. We sampled four intertidal zones across 22 salt marshes along a 650 km stretch of coast in the UK to examine the impact of livestock density on globally important saltmarsh “blue carbon” stocks. Although there were marked impacts of grazing pressure on above ground vegetation composition, structure and biomass, there was no detectable relationship between grazing intensity and soil organic carbon, irrespective of tidal zone in the marsh or soil depth-layer analyzed. A substantial spatial variation in soil carbon was instead explained by contextual environmental variables. There was evidence that compensatory responses by vegetation, such as increased root growth, countered carbon loss from grazing impacts. Our work suggests that grazing effects on carbon stocks are minimal on broader scales in comparison with the influence of environmental context. The benefits of grazing management to carbon stores are likely to be highly context dependent

Flutuações diárias na associação de peixes da praia de areia de Porto Pim, ilha de Faial, Açores

Os peixes da praia de areia de Porto Pim, Açores foram amostrados através de arrastos de rede (chinchorro) a intervalos de três horas durante um período de 24 horas nos meses de Agosto, Setembro e Outubro de 1989. A associação de peixes era dominada, em cada um dos meses, por três a quatro espécies (90-97% dos indivíduos). A maioria das espécies estavam representadas por formas juvenis. A variação entre meses do padrão diário pode explicar-se primariamente pelas mudanças no padrão de abundância das espécies dominantes. Ao longo dos três meses as variações na estrutura da associação implicaram mudanças no padrão diário. Muitas das espécies tinham um padrão de abundância definido, primariamente por ser ou diurno ou nocturno. Encontrou-se também um padrão de maré na estrutura da associação de peixes caracterizado por uma maior diversidade na maré baixa.ABSTRACT: The shallow-water fish assemblage at Porto Pim, Azores was sampled with a beach seine at three hour intervals over 24 h periods in August, September and October 1989. The fish assemblage was dominated by three to four species in each month (90-97% of numbers). Most species were present as juveniles. The variation in diel patterns between months could primarily be explained by changes in the pattern of abundance of dominant species. Over the three months seasonal changes in the assemblage structure caused changes in the diel pattern. Many of the species present had a definite pattern to their abundance being either primarily diurnal or nocturnal. There was also a tidal pattern to the assemblage structure which had a higher diversity at low water

Associações de peixes das zonas entre-marés da ilha do Faial, Açores

No presente artigo descrevemos as associações de peixes das poças do intertidal rochoso e do intertidal arenoso dos Açores. São treze as espécies que ocorrem nas poças do intertidal rochoso. Os blenídeos, com Parablennius sanguinolentus parvicornis, Coryphoblennius galerita e Lipophrys trigloides, constituem a família dominante de peixes residentes das poças do intertidal rochoso. A riqueza é maior no 3º trimestre, com 12 espécies, e menor no 1º trimestre com apenas oito espécies a ocorrerem nas poças. A diversidade é também superior no 3º trimestre. O pequeno grau de variação pode ser fundamentalmente atribuído à presença de espécies transientes e de juvenis que utilizam a costa durante as primeiras fases de desenvolvimento. São quinze as espécies que ocorrem na zona intertidal da praia arenosa de Porto Pim. A comunidade de peixes é aqui dominada por juvenis de espécies transientes. Não encontrámos espécies intertidais residentes. A riqueza e abundância são superiores no 3º e 4º trimestre devido ao recrutamento de juvenis, e à ocorrência de espécies migradoras e transientes.ABSTRACT: In the present paper we describe fish assemblages of rocky intertidal pools and intertidal areas of sandy beaches of the Azores. Blennies (Parablennius sanguinolentus parvicornis, Coryphoblennius galerita and Lipophrys trigloides) constitute the dominant resident fish family in the intertidal pools. Thirteen species were encountered in intertidal pools. Richness is higher in the 3rd quarter of the year with 12 species and lower in the 1st and 2nd quarters with 8 species occurring in the samples . Diversity is also higher in the 3rd quarter The small variation can mostly be attributed to transient species and juveniles using the shore as a nursery ground. Fifteen species occurred in the intertidal region of the protected shallow sandy beach of Porto Pim. This fish assemblage was dominated by juveniles of transient species. No resident species were present here. Richness and abundance were higher in 3rd and 4th quarters due to recruitment of juveniles, and the occurrence of migrant and transient species

The role of kelp species as biogenic habitat formers in coastal marine ecosystems

Kelps are ecologically important primary producers and ecosystem engineers, and play a central role in structuring nearshore temperate habitats. They play an important role in nutrient cycling, energy capture and transfer, and provide biogenic coastal defence. Kelps also provide extensive substrata for colonising organisms, ameliorate conditions for understorey assemblages, and provide three-dimensional habitat structure for a vast array of marine plants and animals, including a number of commercially important species. Here, we review and synthesize existing knowledge on the functioning of kelp species as biogenic habitat providers. We examine biodiversity patterns associated with kelp holdfasts, stipes and blades, as well as the wider understorey habitat, and search for generality between kelp species and biogeographic regions. Environmental factors influencing biogenic habitat provision and the structure of associated assemblages are considered, as are current threats to kelp-dominated ecosystems. Despite considerable variability between species and regions, kelps are key habitat-forming species that support elevated levels of biodiversity, diverse and abundant assemblages and facilitate trophic linkages. Enhanced appreciation and better management of kelp forests are vital for ensuring sustainability of ecological goods and services derived from temperate marine ecosystems

Long-term modifications of coastal defences enhance marine biodiversity

Realization that hard coastal infrastructures support lower biodiversity than natural habitats has prompted a wealth of research seeking to identify design enhancements offering ecological benefits. Some studies showed that artificial structures could be modified to increase levels of diversity. Most studies, however, only considered the short-term ecological effects of such modifications, even though reliance on results from short-term studies may lead to serious misjudgements in conservation. In this study, a seven-year experiment examined how the addition of small pits to otherwise featureless seawalls may enhance the stocks of a highly-exploited limpet. Modified areas of the seawall supported enhanced stocks of limpets seven years after the addition of pits. Modified areas of the seawall also supported a community that differed in the abundance of littorinids, barnacles and macroalgae compared to the controls. Responses to different treatments (numbers and size of pits) were species-specific and, while some species responded directly to differences among treatments, others might have responded indirectly via changes in the distribution of competing species. This type of habitat enhancement can have positive long-lasting effects on the ecology of urban seascapes. Understanding of species interactions could be used to develop a rule-based approach to enhance biodiversity