El límite sur de distribución de Zostera marina L. y Phyllospadix torreyi Watson para el noroeste mexicano

Se analiza el límite sur de distribución de dos angiospermas marinas en México.

Macroalgas epífitas de Zostera marina L. en Bahía Concepción, B.C.S., México

Macroalgas epífitas de Zostera marina L. en Bahía Concepción, B. C. S. México.

Does spatial distribution of fauna depend on algal belts on intertidal boulder fields of the French Basque coast ?

To determine good ecological status and conservation of the Sub-Marine area of the Bay of Biscay, the implementation of a new rocky intertidal habitats monitoring is needed. A protocol has been adapted from the Brittany protocol for the water body FRFC11 "Basque coast" for the two indicators "intertidal macroalgae" and "subtidal macroalgae" under the Water Framework Directive to qualify the ecological. However no protocol has been validated for fauna in front of meridional characters of the benthic communities. Investigations carried out on macroalgae communities on intertidal area in WFD framework, since 2008, constitute an important working basis. This is the aim of the Bigorno project (Intertidal Biodiversity of the south of the Bay of Biscay and Observation for New search and Monitoring for decision support), financed by the Agency of Marine Protected Areas and the Departmental Council. To implement knowledge, a sampling protocol has been used in 2015 on the boulder fields of Guéthary. This site is part of Natura 2000 area "rocky Basque coast and offshore extension "It constitutes also a Znieff site and restricted fishing area. The sampling strategy considers the heterogeneity of substrates and the presence of intertidal microhabitats. Two main habitats are present: "mediolittoral rock in exposed area habitat" and "boulder fields". Habitat "intertidal pools and permanent ponds" is also present but, it is not investigated. Sampling effort is of 353 quadrats of 0.1 m², drawn randomly according to a spatially stratified sampling plan, defined by habitat and algal belts. Taxa identification and enumeration are done on each quadrat. The objective of this work is to expose results from data collected during 2015 sampling program. The importance of characterizing benthic fauna communities spatial distribution belonging to the Basque coast according to algal belts defines during the WDF survey was highlighted. Concurrently, indicators of biodiversity were studied.

Indicator species of intertidal boulder fields on the French Basque coast

The rocky Basque coast presents an interest both in terms of biogeography and its patrimonial situation, alongside its habitats, fauna and flora. The aim of the BIGORNO project (Intertidal Biodiversity of the south of the Bay of Biscay and Observation for New research and Monitoring for decision support), financed by the Agency of Marine Protected Areas (AAMP) and the Departmental Council (CD 64), is to respond to significant deficiencies on biocenosis in the southern marine subregion “Bay of Biscay”. Investigations carried out in the WFD, since 2008, constitute an important basis of work for integration of fauna. Field studies undertaken since 2015 consisting of a sampling design suited to the substrates heterogeneity and the presence of microhabitats were established on an intertidal area specifically on a "Boulder fields" habitat. Assessment was undertaken by sampling quadrats of 0.1 m² drawn randomly from a spatially stratified sampling plan. Our study aims for a better understanding of stratification of this habitat and allowed us to highligh tindicator taxa of the "Boulder fields" habitat. Functions included in the package indicspecies (CRAN) were used to conduct indicator species analysis and to assess the significance of the relationship between taxa or taxa combinations and the habitat. It is therefore possible to describe some species or species groups which are specific to boulder fields through the assessment of their functional traits and local biodiversity. These various analyses allow for a sustainable way of monitoring the Basque intertidal rocky shore.

Home sweet home: evidence for nest-fidelity in the rocky intertidal fish, the shanny Lipophrys pholis

The ability to be faithful to a particular area or site was analysed in the shanny Lipophrys pholis. Using passive integrated transponders, adults from a population of L. pholis at Cabo Raso, Portugal, were followed over a period of 3 years. The findings showed that site fidelity is a consistent behaviour during the breeding season with specific breeding males being found only in particular sectors within the area, and in specific nests throughout the years. The fact that, in general, L. pholis individuals were absent from the study area during the non-breeding season and breeding males were recorded returning to the same nests and sectors for consecutive breeding seasons suggests that they have developed excellent homing abilities. Translocation data corroborate this idea showing that breeding males successfully returned to their nests after a displacement of >100 m. Altogether, these findings highlight the relevance of life-history traits (e.g. nesting) in the conditioning of site fidelity and homing for this species of rocky intertidal fish, and more importantly, provide evidence for the need of a well-developed navigational system.

Environmental and grazing influence on spatial variability of intertidal biofilm on subtropical rocky shores

Epilithic biofilm on rocky shores is regulated by physico-chemical and biological factors and is important as a source of food for benthic organisms. The influences of environmental and grazing pressure on spatial variability of biomass of biofilm were evaluated on shores on the north coast of São Paulo State (SE Brazil). A general trend of greater abundance of microalgae was observed lower on the shore, but neither of the environmental factors evaluated (wave exposure and shore level) showed consistent effects, and differences were found among specific shores or times (September 2007 and March 2008). The abundance of slow-moving grazers (limpets and littorinids) showed a negative correlation with chlorophyll a concentration on shores. However, experimental exclusion of these grazers failed to show consistent results at small spatial scales. Observations of divergent abundances of the isopod Ligia exotica and biomass of biofilm on isolated boulders on shores led to a short exclusion experiment, where the grazing pressure by L. exotica significantly decreased microalgal biomass. The result suggests that grazing activities of this fast-moving consumer probably mask the influence of slow-moving grazers at small spatial scales, while both have an additive effect at larger scales that masks environmental influences. This is the first evaluation of the impact of the fast-moving herbivore L. exotica on microalgal biomass on rocky shores and opens an interesting discussion about the role of these organisms in subtropical coastal environments.

Hydrodynamism and its influence on the density of the decorator crab Microphrys bicornutus (Mithracidae) on intertidal rocky shores from a subtropical region

Hydrodynamism is an environmental stressor on marine communities with effects on populations of intertidal organisms. Microphrys bicornutus is a crab species associated with secondary substrates on rocky shores and little is known about its population dynamics and its relation to the shore hydrodynamics. The aim of this study is to describe the population structure of Microphrys bicornutus on intertidal rocky shores from the north coast of the São Paulo State, Brazil, and the influence of wave exposure on the density of this decorator crab. There was a greater density of M. bicornutus on sheltered than on exposed rocky shores, which is probably due to the hydrodynamic influence on M. bicornutus populations on rocky shores: directly ( by the physical stress caused by wave impact) and indirectly ( by determining the dominance of the secondary substrate) acting on the density of these crabs. Our results also suggest a vertical distribution of juveniles and adults, where the juveniles might be more abundant on the infralittoral fringe and, thus, more influenced by hydrodynamism than adults in the infralittoral.

Natural recovery of the benthic nematode assemblages associated to Zostera noltii seagrass beds after physical disturbance caused by digging harvest activity

Seagrass beds are productive ecosystems that maintain high levels of biodiversity, making them susceptible to anthropogenic pressures such as bivalve harvesting. Nematodes are considered great ecological indicators as changes in their density, diversity and structure may represent changes in the environment. This experimental fieldwork aimed to assess the impact of the bivalve harvesting on the nematodes assemblage of a seagrass bed in the Mira estuary by simulating the digging activity. Two plots were subjected to the digging (D1 and D19) and two plots were control (C11 and C18). The sampling took place in five occasions: T0 – before digging; T1 – 14 days; T2 – 45 days; T3 – 75 days; and T4 – 165 days after digging. The results showed no significant difference in the nematode assemblages’ density, diversity and trophic composition between treatments and sampling times, evidencing their high tolerance for naturally stressed environments and to the level of digging they were exposed; Recuperação natural das comunidades de nematodes bentónicos associados aos povoamentos de Zostera noltii após atividade de marisqueio Resumo: As pradarias marinhas são ecossistemas produtivos que suportam elevados níveis de biodiversidade, pelo que estão sujeitos a pressões antropogénicas. Os nematodes são bons indicadores ecológicos pois respondem rapidamente a qualquer perturbação por alterações na densidade, diversidade e estrutura. Este trabalho experimental teve como finalidade o estudo da recuperação natural das comunidades de nematodes associados aos povoamentos de Zostera noltii pela simulação da atividade de marisqueio. Dois plots foram sujeitos a revolvimento (D1 e D19) e dois plots serviram como controlo (C11 e C18) e foram efetuadas amostragens em cinco ocasiões: T0 – antes do revolvimento; T1 – 14 dias; T2 – 45 dias; T3 – 75 dias; e T4 – 165 dias após revolvimento. Os resultados obtidos não mostraram diferenças significativas na diversidade, densidade e composição trófica das comunidades de nematodes entre tratamentos e tempos de amostragem, evidenciando a sua elevada tolerância a ambientes naturalmente dinâmicos e ao nível de revolvimento a que foram expostas.

Fish assemblages of shallow intertidal habitats of the Ria Formosa lagoon (South Portugal): influence of habitat and season

Fish assemblages in seagrass and unvegetated habitats located in shallow intertidal creeks within the saltmarsh area of the Ria Formosa coastal lagoon were sampled with a Riley push net at 3 sites on a monthly basis over a 1 yr period. The objective was to test if both habitats support similar fish assemblages in terms of abundance, diversity, assemblage structure, and size distribution, and to investigate how site and season affect the assemblages. Fish assemblages associated with these habitats were significantly different in terms of diversity, abundance, and assemblage structure. Seagrass supported a larger number of species and greater diversity, while unvegetated habitat supported greater fish numbers but only of a few species. The habitats were dominated by different groups of resident species that were responsible for major differences in fish assemblage structure between habitats. Pomatoschistus microps and young-of-the-year (YOY) Atherina presbyter dominated the unvegetated habitat, while seagrass was dominated by a diverse group of species, in particular syngnathids and small labrids, revealing different habitat preferences. Site and season were determinant factors conditioning the role of habitat in structuring fish assemblages. Distance between habitats, site elevation, and the amount of marsh drained affected fish assemblages in both habitats. Seasonal fluctuations in the presence and abundance of YOY from marine migrant and resident species were responsible for comparable changes in fish assemblage structure in both habitats. Both habitats provide a distinctive nursery area for different species, while common species reveal ontogenic distributional changes between habitats, where smaller fish appear first in unvegetated creeks.

Living on the intertidal/subtidal edge: ecology of the stalked barnacle Pollicipes Pollicipes and of the sea urchin Paracentrotus lividus

This thesis contributes to the knowledge of temperate rocky shore ecology, with direct implications in the management and conservation of two important local marine resources that inhabit the very edge of subtidal and intertidal habitats on wave-swept rocky shores: the sessile filter feeding stalked barnacle Pollicipes pollicipes and the mobile keystone herbivore sea urchin Paracentrotus lividus. Research was conducted along gradients of wave exposure on rocky shores of Southern Europe. The abundance of P. lividus was four times higher in SW Portugal than in NW Italy. Most of the variation in urchin abundance occurred at small spatial scales, probably shaped by habitat complexity. In SW Portugal, sea urchin attachment forces while in burrows were measured and related to burrow shape, urchin size and habitat. Burrowing behaviour enhances sea urchin attachment force and might be an adaptive response to hydrodynamic stress. Abundance of P. pollicipes in SW Portugal is highly and positively related to wave exposure at local and regional scales. Predation and recruitment processes seem to be important drivers of these abundance patterns. A distribution model of P. pollicipes abundance in relation to wave exposure was developed for the SW coast of Portugal and might be used for improvement of its management and conservation. Growth of P. pollicipes was studied by applying a novel method using fluorescent calcein for marking and to estimate growth. Growth rate decreased with barnacle size and was highly variable amongst individuals, particularly in smaller barnacles. No effect of shore level on barnacle growth was detected. An assessment of the state of the fishery, conservation and management of the stalked barnacle in different regions of continental Portugal was made, highlighting an overall negative tendency of this state and recommending a change into a co-management system; Resumo: Viver no limite intertidal / subtidal: ecologia do percebe Pollicipes pollicipes e do ouriço-do-mar Paracentrotus lividus Esta tese contribui para o conhecimento da ecologia do litoral rochoso e tem implicações diretas na gestão e conservação de dois recursos marinhos locais que habitam o interface subtidal/intertidal de costas rochosas sujeitas a agitação marinha: o percebe Pollicipes pollicipes, animal séssil e filtrador e o ouriço-do-mar Paracentrotus lividus, animal móvel e herbívoro. Foram realizados vários estudos ao longo de gradientes de hidrodinamismo em costas rochosas do sul da Europa. A abundância de P. lividus foi quatro vezes superior no sudoeste de Portugal relativamente ao noroeste de Itália. Grande parte da variação na abundância de P. lividus ocorreu a pequenas escalas espaciais, provavelmente influenciada pela complexidade do habitat. A força com que o ouriço-do-mar se fixa ao substrato foi medida no terreno no sudoeste de Portugal, tendo esta sido relacionada com a forma da depressão que ocupa, o tamanho individual e o habitat. O comportamento escavador desta espécie aumenta a sua força de fixação ao substrato e poderá ser uma resposta adaptativa ao hidrodinamismo.. A abundância de P. pollicipes na costa sudoeste de Portugal, a diferentes escalas espaciais, está relacionada de forma positiva com a agitação marinha, e é influenciada pela predação e pelo recrutamento desta espécie. Foi desenvolvido um modelo de distribuição e abundância de P. pollicipes para esta costa baseado na relação com a agitação marinha, cujos resultados podem ser usados para melhorar a gestão e conservação deste recurso. Um novo método com recurso a calceina fluorescente foi desenvolvido para marcar percebes e estudar o seu crescimento. A taxa de crescimento diminuiu com o tamanho do animal, sendo altamente variável entre indivíduos, sobretudos nos de menores dimensões. O estado da apanha, conservação e gestão do percebe em diferentes regiões de Portugal Continental apresentou uma tendência global negativa, e recomenda-se uma alteração para um sistema de cogestão deste recurso.

Benthic nematode assemblage composition and diversity during a natural recovery process of Zostera noltii seagrass beds,

In 2008, the stable seagrass beds of the Mira estuary (SW Portugal) disappeared completely; however, during 2009, they have begun to present early symptoms of natural recovery, characterised by a strongly heterogeneous distribution. This study was designed to investigate the spatial and temporal variability patterns of species composition, densities and trophic composition of the benthic nematode assemblages in this early recovery process, at two sampling sites with three stations each and at five sampling occasions. Because of the erratic and highly patchy seagrass recovery and the high environmental similarity of the two sampling sites, we expected within-site variability in nematode assemblages to exceed between-site variability. However, contrary to that expectation, whilst nematode genus composition was broadly similar between sites, nematode densities differed significantly between sites, and this between-site variability exceeded within-site variability. This may be linked to differences in the Zostera recovery patterns between both sites. In addition, no clear temporal patterns of nematode density, trophic composition and diversity were evident.

Effects of human trampling on a rocky shore fauna on the Sao Paulo coast, southeastern Brazil

Increased tourist activity in coastal regions demands management strategies to reduce impacts on rocky shores. The highly populated coastal areas in southeastern Brazil are an example of degradation caused by development of industry and tourism. Among different shore impacts, trampling has been intensively studied, and may represent a significant source of stress for intertidal fauna. A randomised blocks design was applied to experimentally study the effects of two different trampling intensities on richness, diversity, density and biomass of the rocky shore fauna of Obuseiro beach, Guarujá, southeastern Brazil. Blocks were distributed in two portions of the intertidal zone, dominated respectively by Chthamalus bisinuatus (Cirripedia) and Isognomon bicolor (Bivalvia). Blocks were trampled over three months, simulating the vacation period in Brazil and were monitored for the following nine months. Results indicate that Chthamalus bisinuatus is vulnerable to trampling impacts. Richness, diversity and turn-over index tended to be higher in trampled plots four months after trampling ceased. In general, results agree with previous trampling studies, suggesting that even low intensities of trampling may cause some impact on intertidal communities. Management strategies should include isolation of sensitive areas, construction of boardwalks, visitor education and monitoring programmes. In Brazil, additional data obtained from experimental studies are necessary in order to achieve a better understanding of trampling impacts on rocky shore communities.

Effects of temperature and salinity on the survival rates of coxicerberus ramosae (Albuquerque, 1978), an interstitial isopod of a Sandy Beach on the coast of Brazil

The tolerance to the combined effects of temperature and salinity was investigated in the interstitial isopod Coxicerberus ramosae (Albuquerque, 1978), a species of intertidal zone of sandy beaches in Rio de Janeiro, Brazil. The animals were collected on Praia Vermelha Beach. The experiments lasted 24 h and nine salinities and seven temperatures were used for a total of 63 combinations. Thirty animals were tested in each combination. The species showed high survival in most of the combinations. The temperature of 35 ºC was lethal and at 5 ºC, the animals tolerated only a narrow range of salinities. The statistical analyses showed that the effects of temperature and salinity were significant on the survival, which confirmed the euryhalinity and eurythermy of this species.