208 research outputs found
Spatial variation of reef fishes and the relative influence of biotic and abiotic habitat traits
Patterns of distribution of reef fishes were examined across three spatial scales and related to habitat traits along
25 km of the northern Portuguese coast. Response variables included the multivariate assemblage structure, the total
number of taxa and individuals, and the abundance of single groups categorized according to their preference for
the benthic, proximo-benthic or pelagic environment, feeding and reproductive behaviour. Habitat traits included
topographic elements (small and large âdropsâ like cracks and crevices) and the extent of dominant morpho-functional
types of macroalgae (kelp, large foliose, small erect, turf-forming filamentous, and encrusting). All fish responses were
characterized by the largest variance at the smallest scale (among transects tens m apart), followed by that among
reefs (hundreds m to 1 km apart) and almost null variance among sites (some km apart). Small and large âdropsâ of
the substratum explained, respectively, considerable variation of assemblage structure and the total abundance of
individuals, while the extent of bare rock influenced the richness of taxa and that of benthic fishes, fishes feeding on
sessile invertebrates and fishes laying benthic eggs or having nesting behaviour. Combinations of abiotic and biotic
structural attributes of reefs influenced proximo-benthic fishes, the predators of mobile animals and fishes releasing
pelagic eggs. The here reported associations between patterns of distribution of reef fishes and habitat traits have
implications for the design of future protection schemes suitable to guarantee the conservation of reef fish communities
and of the processes responsible for their variation. Within the SLOSS (single-large vs. several-small) debate in the
design of marine reserves, for example, effective protection to the studied reef fishes would be provided by a set of
small reserves, rather than a single large which might be appropriate for fishes having wider home ranges
Spatial variation of reef fishes and the relative influence of biotic and abiotic habitat traits
Abstract Patterns of distribution of reef fishes were examined across three spatial scales and related to habitat traits along 25 km of the northern Portuguese coast. Response variables included the multivariate assemblage structure, the total number of taxa and individuals, and the abundance of single groups categorized according to their preference for the benthic, proximo-benthic or pelagic environment, feeding and reproductive behaviour. Habitat traits included topographic elements (small and large 'drops' like cracks and crevices) and the extent of dominant morpho-functional types of macroalgae (kelp, large foliose, small erect, turf-forming filamentous, and encrusting). All fish responses were characterized by the largest variance at the smallest scale (among transects tens m apart), followed by that among reefs (hundreds m to 1 km apart) and almost null variance among sites (some km apart). Small and large 'drops' of the substratum explained, respectively, considerable variation of assemblage structure and the total abundance of individuals, while the extent of bare rock influenced the richness of taxa and that of benthic fishes, fishes feeding on sessile invertebrates and fishes laying benthic eggs or having nesting behaviour. Combinations of abiotic and biotic structural attributes of reefs influenced proximo-benthic fishes, the predators of mobile animals and fishes releasing pelagic eggs. The here reported associations between patterns of distribution of reef fishes and habitat traits have implications for the design of future protection schemes suitable to guarantee the conservation of reef fish communities and of the processes responsible for their variation. Within the SLOSS (single-large vs. several-small) debate in the design of marine reserves, for example, effective protection to the studied reef fishes would be provided by a set of small reserves, rather than a single large which might be appropriate for fishes having wider home ranges
Potential effects of kelp species on local fisheries
1. Kelp species are ecosystem engineers in temperate coasts, where they provide valuable services
to humans. Evidence of the declines of kelp forests exists from several regions, but their
effects on fisheries still need to be elucidated. More effective management strategies for sustainable
fisheries require a synthesis of research findings and an assessment of how research
could be improved to fill current gaps.
2. This review aimed to: (i) summarize the available evidence on the influence of changes in
kelp density and/or area on the abundance and diversity of associated fisheries and (ii) examine
how research on kelpâfisheries interactions could better support effective management.
3. Most studies (67%) reported data ascribable, directly or indirectly, to a positive relationship
between kelp and fishery-relevant variables, 11% provided evidence of a negative relationship,
15% indicated species-specific findings and the remaining found unclear or âneutralâ
relationships.
4. Important shortcomings were identified, including the paucity of experimental studies suitable
to test for unequivocal causeâeffect relationships, the disproportion between North America,
which is well-studied, and other regions and between the large number of fish-based
investigations and the small number of those focusing on other commercially important organisms,
and the general lack of studies carried out over spatial and temporal scales comparable to
those of global processes driving patterns of distribution of both kelps and fisheries.
5. Synthesis and applications. The consistency of most studies in showing a positive kelpâfishery
relationship supports the protection of kelp habitats stated by current environmental
directives. However, achieving their goals requires that the limitations we detect are
addressed through better connections between research, management practice and policy.
This would require the following: (i) researchers to combine multiple approaches (large-scale
experimental studies and modelling) for the analysis of kelpâfisheries relationships; (ii) funding
agencies to provide resources needed to fill the existing gaps; and (iii) researchers and
institutions from less studied regions to strengthen collaborations with those from regions
where there have been more investigations into kelpâfishery systems. This is essential under
present and predicted environmental changes, with the ultimate aim of conserving and allowing
the sustainable use of critically important habitats and of fishery resources relying on
these
Compounded perturbations in coastal areas: contrasting responses to nutrient enrichment and the regime of storm-related disturbance depend on life-history traits
1. Natural systems are exposed to compounded perturbations, whose changes in temporal
variance can be as important as those in mean intensity for shaping the structure of assemblages.
Specifically, climate-related physical disturbances and nutrient inputs due to natural
and/or anthropogenic activities occur concomitantly, but experimental tests of the simultaneous
effects of changes in the regime of more than one perturbation are generally lacking.
Filling this gap is the key to understand ecological responses of natural assemblages to
climate-related change in the intensity and temporal patterning of physical disturbance combined
with other global stressors.
2. Responses to factorial manipulations of nutrient enrichment, mean intensity and temporal
variability in storm-like mechanical disturbance were examined, using benthic assemblages of
tide-pools as model system.
3. Response variables were mean abundance values and temporal variances of taxa with different
life-traits. Consistent negative effects of disturbance intensity were observed for the mean
cover of long-living taxa (algal canopies and the polychaete Sabellaria alveolata), whose temporal
fluctuations were also reduced by more severe mechanical stress. More resilient taxa
(ephemeral algae, mostly green of the genus Ulva) increased under enriched conditions, particularly
when low-intensity events were irregularly applied over time. Opposite effects of disturbance
intensity depending on nutrient availability occurred on filamentous algae (e.g. red of
the genus Ceramium). This was probably due to the fact that, although nutrient enrichment
stimulated the abundance of both algal groups, when this condition was combined with relatively
mild physical disturbance the competitively superior ephemeral green algae tended to
become dominant over filamentous red algae. The same did not occur under high intensity of
disturbance since it likely damaged large, foliose fronds of Ulva-like forms more than small, filamentous
fronds of Ceramium-like forms. Grazers were positively affected by nutrients, likely
responding indirectly to more food available.
4. A direct relationship between the mean abundance of most organisms and their temporal
fluctuations was documented. However, all organisms persisted throughout the study, even
under experimental conditions associated to the largest temporal variation in their abundance,
likely due to their ability to resist to/quickly recover from, the applied perturbations. Therefore,
in systems with great recovery abilities of dominant organisms (e.g. rocky intertidal,
grasslands), effects of traits of the regime of disturbance and nutrient enrichment may modulate the fluctuations of populations not through the elimination and substitution of species,
but through changes in relative abundances of the same species. This contrasts with the
theory that temporal variation in abundance would be directly related to the risk of local
extinction. Present findings enable more accurate predictions of the consequences of climatic
and non-climatic scenarios on the biodiversity of marine and terrestrial systems sharing analogous
functional traits of organisms. Future more intense physical disturbances are expected to
exert negative effects on slow-growing/recovering species (e.g. habitat-formers) irrespectively of
the temporal patterning of the same disturbances and nutrient inputs. On the contrary, more
resistant species (e.g. encrusting algae on rocky shores or below-ground vegetation in grasslands)
are expected to benefit from intense physical disturbance. Species whose abundance is
more directly related to the availability of nutrients (e.g. filamentous and ephemeral algae or
herbs) are expected to generally increase under enriched conditions, but their ability to eventually
become dominant would depend on their ability to grow fast and attain cover large
enough to overwhelm any possible control of concomitant disturbance intensity on their abundance.
If, such as in the present examined system, virtually all organisms can persist, over the
temporal scale of the experiment, under any combination of physical disturbance and nutrient
availability, the resulting overall diversity is not predicted to change drastically. Nevertheless,
low-intensity events evenly distributed and high-intensity events irregularly distributed appear
as the conditions supporting the highest richness of taxa, independently of the availability of
nutrients
The amphipod assemblages of Sabellaria alveolata reefs from the NW coast of Portugal: An account of the present knowledge, new records, and some biogeographic considerations
Amphipod assemblages associated with the biogenic reefs built by the honeycomb worm Sabellaria alveolata were studied at two sites (Praia da Aguda and Belinho) along the northwestern coast of Portugal. A total of 3909 specimens were collected, comprising 14 different amphipod species. A first record from the northeastern Atlantic coast was registered here for the species Caprella santosrosai, which was, up to now, recorded only along the Mediterranean coast of the Iberian Peninsula. A male specimen collected from the Sabellaria-reef located in Belinho allowed an update to the known distribution of C. santosrosai, thus altering its previous status as an endemic Mediterranean species. The most common species collected during the study were Microdeutopus chelifer (n = 1828), Jassa ocia (n = 1426), and Hyale stebbingi (n = 452). Forty-three percent of the total recorded species were encountered in both study sites, whereas the remaining 57 % were restricted to a single site (Belinho). The majority of the collected species (93 %) showed an Atlantic-Mediterranean distribution, confirming the close affinity between eastern Atlantic and Mediterranean amphipod assemblages and the role of the Portuguese coast as a transition zone through which numerous warm-water species, coming from North Africa and the Mediterranean Sea, could enter into the Atlantic and possibly get mixed with species coming from the North Sea and the Arctic, typically having affinity for colder waters
Connell and Slatyer's models of succession in the biodiversity era
Understanding how species interactions drive succession is a key issue in
ecology. In this study we show the utility of combining the concepts and methodologies
developed within the biodiversityâecosystem functioning research program with J. H. Connell
and R. O. Slatyerâs classic framework to understand succession in assemblages where multiple
interactions between early and late colonists may include both inhibitory and facilitative
effects. We assessed the net effect of multiple species interactions on successional changes by
manipulating the richness, composition, and abundance of early colonists in a low-shore
assemblage of algae and invertebrates of the northwestern Mediterranean. Results revealed
how concomitant changes in species richness and abundance can strongly alter the net effect of
inhibitory vs. facilitative interactions on succession. Increasing richness of early colonists
inhibited succession, but only under high levels of initial abundance, probably reflecting the
formation of a highly intricate matrix that prevented further colonization. In contrast,
increasing initial abundance of early colonists tended to facilitate succession under low
richness. Thus, changes in abundance of early colonists mediated the effects of richness on
succession
The role of environmental conditions in regulating long-term dynamics of an invasive seaweed
The mechanisms underpinning long-term dynamics and viability of invader populations in the receiving environment remain largely unknown. We tested the hypothesis that temporal variations in the abundance of a well-established invasive seaweed, Caulerpa cylindracea, in the NW Mediterranean, could be regulated by inter-annual fluctuations in environmental conditions. Abundance data of C. cylindracea, sampled repeatedly between 2005 and 2020 at the peak of its growing season (late summer/early fall), were related to interannual variations in seasonal seawater temperature, wind speed and rainfall recorded during different growth phases of the alga, in both subtidal and intertidal habitats. In both habitats, higher peak of C. cylindracea cover was associated with lower seawater temperature in spring and summer, when the seaweed exits the winter resting phase and starts a period of active growth. In addition, the peak abundance of subtidal C. cylindracea was positively associated with higher autumn wind speed intensity and spring daily total precipitation. Our study reveals the importance of seasonal and interannual variation of abiotic factors in shaping temporal patterns of abundance of C. cylindracea, in both subtidal and intertidal habitats. Identifying the factors underpinning invasive population temporal dynamics and viability is essential to predict the time and conditions under which an invader can thrive, and thus guide management strategies aimed to containing invasions under current and future climates
Benthic assemblages of rock pools in northern Portugal: seasonal and between-pools variability
We investigated the seasonal (winter vs summer and within season) and spatial (between-pool) variability of benthic assemblages of rock pools at mid-intertidal level along the shore of Viana do Castelo (North Portugal). Physical traits of rock pools, including size, depth and position along the shore, were also compared between pools. While pools did not differ for any of the examined physical traits, results indicated a clear seasonal difference in the structure of assemblages, including a total of 49 macroalgal and 13 animal taxa. This finding was driven by six taxa that are more abundant in winter (the reef-forming polychaete Sabellaria alveolata, the articulated coralline algae Corallina spp., the brown alga Bifurcaria bifurcata, the encrusting coralline alga Lithophyllum incrustans, the red alga Chondracanthus acicularis and the grazing snails Gibbula spp.) and four algal taxa that are more abundant in summer (the invasive brown Sargassum muticum, the green Ulva spp., the kelp Laminaria ochroleuca and the filamentous red Ceramium spp.). These data provide a new contribution to the knowledge of rock pool systems and have potential implications for monitoring programmes aimed at assessing ecological modifications related to natural and anthropogenic disturbances and for identifying processes responsible for the variability of rock pool assemblages
Herbivory drives kelp recruits into âhidingâ in a warm ocean climate
Assessing effects of herbivory across broad gradients of varying ocean climate conditions and over small spatial scales is crucial for understand- ing its influence on primary producers. Effects of her- bivory on the distribution and abundance of kelp re- cruits were examined experimentally at two regions under contrasting ocean climate. Specifically, the abundance and survivorship of kelp recruits and the abundance of macro-herbivores were compared be- tween a âcoolâ and a âwarmâ region in northern and central Portugal, respectively. In each region, the abundance of kelp recruits and the intensity of grazing were compared between habitats of different topography within reefs (open reef vs. crevices). Com- pared to the âwarmâ region, the abundance of kelp re- cruits was 3.9 times greater in the âcoolâ region, where 85% of recruits were found in open reef habitats. In contrast, 87% of recruits in the âwarmâ region were re- stricted to crevices. The âwarmâ region had 140 times greater abundances of sea urchins, 45 times more herbivorous fish and 4.1 times more grazing marks on kelp recruits than the âcoolâ region. Grazing assays showed ca. 50 times higher rates of kelp biomass con- sumption, mainly by fishes, and zero survivorship of kelp recruits in the âwarmâ relative to the âcoolâ region. This study suggests both temperature and herbivores affect abundances of kelp recruits across latitudes, and demonstrates how herbivores affect their distri- bution at local scales, driving kelp recruits into âhidingâ in crevices under intense herbivory. Conse- quently, where net recruitment success is compro- mised by herbivory, the persistence of kelps will be contingent on availability of topographical refuges
Morphological and molecular responses of the sea urchin Paracentrotus lividus to highly contaminated marine sediments: The case study of Bagnoli-Coroglio brownfield (Mediterranean Sea)
none8noMarine sediments store complex mixtures of compounds, including heavy metals, organotins and a large array of other contaminants. Sediment quality monitoring, characterization and management are priorities, due to potential impacts of the above compounds on coastal waters and their biota, especially in cases of pollutants released during dredging activities. Harbours and marinas, as well as estuaries and bays, where limited exchanges of water occurr, the accumulation of toxic compounds poses major concerns for human and environmental health. Here we report the effects of highly contaminated sediments from the site of national interest Bagnoli-Coroglio (Tyrrhenian Sea, Western Mediterranean) on the sea urchin Paracentrotus lividus, considered a good model for ecotoxicological studies. Adult sea urchins were reared one month in aquaria in the presence of contaminated sediment that was experimentally subject to different patterns of re-suspension events (mimicking the effect of natural storms occurring in the field), crossed with O2 enrichment versus natural gas exchanges in the water. The development of embryos deriving from adult urchins exposed to such experimental conditions was followed until the pluteus stage, checking the power of contaminated sediment to induce morphological malformations and its eventual buffering by high oxygenation. Real-Time qPCR analysis revealed that the expression of several genes (among the fifty analyzed, involved in different functional processes) was targeted by contaminated sediments more than those exposed in oxygen-enriched condition. Our findings have biological and ecological relevance in terms of assessing the actual impact on local organisms of chronic environmental contamination by heavy metals and polycyclic aromatic hydrocarbons affecting the Bagnoli-Coroglio area, and of exploring enhanced sediment and water oxygenation as a promising tool to mitigate the effects of contamination in future environmental restoration actions.embargoed_20220101Ruocco N.; Bertocci I.; Munari M.; Musco L.; Caramiello D.; Danovaro R.; Zupo V.; Costantini M.Ruocco, N.; Bertocci, I.; Munari, M.; Musco, L.; Caramiello, D.; Danovaro, R.; Zupo, V.; Costantini, M
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