Sheltered Sites Research Articles

Local conditions modulated the effects of marine heatwaves on coral bleaching in subtropical Hong Kong waters

A mass coral bleaching event occurred in the summer of 2022 in subtropical Hong Kong, driven by two marine heatwaves (MHWs) with high intensities of 1.56 and 0.86 °C above a mean climate condition, both MHWs 7 days with a short gap of 4 days during the strong La Niña year. A transect survey was conducted at nine study sites in three regions, which revealed widespread coral bleaching with bleached coral cover ranging from 2.4 to 70.3%. In situ environmental data revealed the presence of a thermocline and halocline. Local conditions, including depth and wave exposure, significantly influenced the bleaching response. Shallow-water (2–4 m) corals were primarily affected, particularly in sheltered and moderately sheltered sites that exhibited higher levels of bleached coral cover (42.97 ± 15.4% and 44.93 ± 29.4%, respectively) compared to the exposed sites (31.8 ± 5.2%). Bleaching in deep waters (4–6 m) was minimal, with only a few colonies of Goniopora at two of the three sheltered sites exhibiting bleaching (1.7 ± 1.5%). Heat stress resistance differed between coral genera. Recovery rate for four common coral genera is low for Acropora tumida. Additionally, a minor hypoxia event was found to cause mortality of non-coral benthos at a sheltered site (Sharp Island). These findings highlight the alarming impact of extreme heatwaves on subtropical coral communities and underscore the importance of monitoring coral bleaching.

The chemical state of the watershed in Ras Elma region (South of Taza, Morocco) one of the parameters responsible for the decline in the formation of the current travertine formations.

The Ras Elma region, situated to the south of the city of Taza in northern Morocco, boasts abundant travertine formations that continue to develop, albeit selectively in specific sheltered sites. This development is influenced by various parameters, including the role of water chemistry. This article presents a spatio-temporal analysis of various hydrochemical parameters, including conductivity, pH, temperature, magnesium, calcium, and others. It's worth noting that the water from the Ras Elma Vauclusian spring, a key driver of travertinization in the region, is sourced from water infiltrating through faults and flowing into Lake Tompraire, known as Dayat Chikker near the Bab Boudir area. The findings suggest that the water in Ras Elma has turned aggressive, as revealed by the examination of the calcaro-carbonic equilibrium. CaCO3 precipitation occurs predominantly in the summer, significantly impacting the formation of travertines, particularly those of the spring and dam types. However, valley-type travertines exhibit more extensive development compared to the other two types.

The Jojosi Dongas: An interdisciplinary project to study the evolution of human behaviour and landscapes in open-air contexts

Hunter-gatherer groups conduct most of their activities in open landscapes as they provide drinking water, food, and raw materials, and offer spaces for social gatherings. The remains left behind at such sites allow for unique archaeological insights into the spatial patterning of prehistoric behaviour. The Stone Age record in southern Africa remains best-known from sheltered sites. A paucity of stratified open-air localities precludes understanding the full spectrum of past hominin activities. Here we introduce an interdisciplinary project in KwaZulu-Natal to study the evolution of human behaviour and landscape dynamics during the Pleistocene in the open-air context of a stratified hillslope with sediments exposed in so-called dongas, a landform created by gully erosion. The project encompasses field and laboratory approaches, combining archaeological, geographical, geological, chronometric, and palaeoenvironmental data. After reviewing relevant open-air research in archaeology and geography, we identify the Jojosi Dongas as a promising research area. Our fieldwork results from 2022-2023 demonstrate the high archaeological, geographical, and geological potential of this landscape. Foot surveys found abundant MSA artefacts spread throughout the dongas, one area with ESA tools, but little to no traces of LSA or later material. Most finds lie on the surface with rarer stratified material occurring in exposed profiles. The surface MSA material is characterised by almost exclusive hornfels use, frequent cortical pieces, many large blanks and cores, and rare retouched tools. These features differ markedly from lithic trends observed in well-known shelter sites, likely the result of differences in site function. Based on the nature of the surface assemblages and the presence of a large outcrop of high-quality hornfels, we hypothesise that the Jojosi Dongas may have been a specialised quarry and workshop area. The stratified MSA occupations are the focus of ongoing excavations and further studies will aim to test our preliminary interpretations provided here.

Contrasting the evolution of radiation fog over a heterogeneous region in southwest France during the SOFOG3D campaign

AbstractObservations made during the recent SOuth‐west FOGs 3D experiment (SOFOG3D) have been used to investigate the formation and evolution of radiation fog over heterogeneous forest plantations. The focus was on comparing measurements made at a relatively open site on arable land with those made in an approximately 700‐m diameter field surrounded by tree plantations, with both sites hosting an instrumented 50‐m mast. These data showed that at the more sheltered site radiation fog tended to form earlier than at the more open site. This coincided with more rapid decreases and lower minima in both near‐surface temperatures and vertical turbulence from the late afternoon. It is proposed here that the surrounding forest creates a sheltering effect, which can cause a reduction in vertical turbulence and therefore the mixing of cool near‐surface air with warmer air aloft. The near‐surface region is therefore able to cool rapidly, enabling fog to form more readily. Data from additional sites with varying surroundings supported the findings that the more sheltered sites tended to exhibit lower near‐surface nocturnal temperatures. However, the onset of fog formation observed at these additional sites suggested that there could be a limit to how sheltered a site may be before fog formation is inhibited rather than enabled by the surroundings.

Factors Affecting Family Welfare of Garut-Indonesia Flash Flood Survivors: A Case Study of Impact Disaster on SDGs

Disasters risk reduction and sustainable development goals (SDGs) are closely linked. The frequent disaster causing devastating impact on society and community. This study aims to analyze the driver of family welfare of survivors of the 2016 Garut flash flood. The total sample consisted of 120 families, some living in temporary sheltered evacuation sites (SF) and others having returned home (non-sheltered group/NSF). Data was obtained at the four months following the disaster. The study revealed that, compared to the respondents in the SF sites, the NSF respondents had higher income, more sources of stress, better coping strategies, and a higher level of welfare. Income, financial management, coping strategies, and economic pressure all had a positive effect on total welfare while, in the case of subjective wellbeing, greater impact came from sources of stress compared with coping strategies. Objective wellbeing, on the other hand, was only influenced by income and coping strategies.

A Rational Method for the Design of Sand Dike/Dune Systems at Sheltered Sites; Wadden Sea Coast of Texel, The Netherlands

A rational method for the design of sand dike/dune systems at sheltered sites is presented, focussing on the cross-shore dimensions of the sand dike in relation to the local wave climate, tidal regime and available sandy materials. The example case is the new sand dike/dune system along the south-east coast of Texel, The Netherlands. The old dike protecting the island was not sufficiently strong to withstand an extreme storm event and has been strengthened by a new sand dune/dike. Various empirical and numerical models have been used, compared and validated to determine the erosion volumes during annual conditions and extreme storm events. Potential wind-induced (aeolian) sediment transport and erosion is also studied using the modified Bagnold-equation including the effects of grain size, moisture content and vegetation. The overall design method resulted into an innovative design solution, guarantying a naturally integrated and resilient sand protection as well as optimal coastal safety.

Do ecological traits of low abundance and niche overlap promote hybridisation among coral-reef angelfishes?

Hybridisation among species of coral-reef fish was previously considered to be rare. However, recent studies have revealed that hybridisation is prevalent in coral-reef fish, highlighting the need to understand the causes of this process. The angelfishes (family Pomacanthidae) have the greatest proportion (~ 30%) of hybridising species to date, with 26 species reported to hybridise. The aim of this study was to examine ecological factors (rarity of parent species and niche overlap) that promote hybridisation in terrestrial environments and to test these factors in the marine environment by examining hybridising angelfishes at Christmas Island (Indian Ocean). Three species of pygmy angelfish (Centropyge flavissima, C. eibli, and C. vrolikii) and their hybrids were investigated to address three objectives: (1) to determine temporal and spatial patterns in abundance and whether these patterns are linked to environmental factors; (2) to test for overlapping patterns in habitat use; and (3) to test for overlapping patterns in diet. Based on 14 yr of surveys, C. flavissima was abundant (4.53 individuals per 250 m2 ± 0.66), whereas C. eibli, C. vrolikii, and all hybrid combinations were consistently rare (average abundance < 0.3 per 250 m2 ± 0.03). Parent species and their hybrids were more abundant at 20 m depth compared to 5 m. All species and their hybrids had similar patterns of abundance around Christmas Island, with significantly high abundances evident at the most sheltered sites. Parent species and their hybrids also had similar diets that comprised a mix of green, red, and brown algae. The rarity of parent species, their niche overlap, and the haremic reproductive strategy likely promote hybridisation in angelfishes at Christmas Island. This study provides empirical evidence that hybridisation in reef fishes conforms to terrestrial-based hypothesis, and thus advances our understanding of the processes underlying hybridisation in coral-reef systems.

Intertidal sea stars (Pisaster ochraceus) alter body shape in response to wave action

Sea stars are some of the largest mobile animals able to live in the harsh flow environment of wave-exposed, rocky intertidal shores. In addition, some species, such as the northeastern Pacific Pisaster ochraceus, are ecologically significant predators in a broad range of environments, from sheltered lagoons to the most wave-exposed shorelines. How they function and survive under such an extreme range of wave exposures remains a puzzle. Here we examine the ability of P. ochraceus to alter body form in response to variation in flow conditions. We found that sea stars in wave-exposed sites had narrower arms and were lighter per unit arm length than those from sheltered sites. Body form was tightly correlated with maximum velocity of breaking waves across four sites and also varied over time. In addition, field transplant experiments showed that these differences in shape were due primarily to phenotypic plasticity. Sea stars transplanted from a sheltered site to a more wave-exposed site became lighter per unit arm length, and developed narrower arms, after 3 months. The tight correlation between water flow and morphology suggests that wave force must be a significant selective factor acting on body shape. On exposed shores, narrower arms probably reduce both lift and drag in breaking waves. On protected shores, fatter arms may provide more thermal inertia to resist overheating, or more body volume for gametes. Such plastic changes in body shape represent a unique method by which sea stars adapt to spatial, seasonal and possibly short-term variation in flow conditions.

Estimating surface sublimation losses from snowpacks in a mountain catchment using eddy covariance and turbulent transfer calculations

AbstractSublimation is a critical component of the snow cover mass balance. Although sublimation can be directly measured using eddy covariance (EC), such measurements are relatively uncommon in complex mountainous environments. The EC measurements of surface snowpack sublimation from three consecutive winter seasons (2004, 2005 and 2006) at a wind‐exposed and wind‐sheltered site were analysed to characterise sublimation in mountainous terrain. During the 2006 snow season, snow surface and near‐surface air temperature, humidity and wind were also measured, permitting the calculation of sublimation rates and a comparison with EC measurements. This comparison showed that measured and simulated sublimation was very similar at the exposed site but less so at the sheltered site. Wind speeds at the exposed site were nearly four times than that at the sheltered site, and the exposed site yielded measured sublimation that was two times the magnitude of that at the sheltered site. The time variation of measured sublimation showed diurnal increases in the early afternoon and increased rates overall as the snow season progressed. Measured mean daily sublimation rates were 0.39 and 0.15 mm day−1 at the exposed and sheltered sites, respectively. At the exposed site, measured sublimation accounted for 16% and 41% of the maximum snow accumulation in 2006 and 2005, respectively. At the sheltered site, measured seasonal sublimation was approximately 4% in 2004 and 2006 and 8% in 2005 of the maximum snow water equivalent. Simulated sublimation was only available for 2006 and suggested smaller but comparable percentages to the sublimation estimated from observations. At the exposed site, a total of 42 mm sublimated for the snow season, which constituted 12% of the maximum accumulation. At the sheltered site, 17 mm (2.2% of maximum accumulation) was sublimated over the snow season. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Byssus secretion of Mytilus galloprovincialis: effect of site at macro- and micro-geographical scales within Ría de Vigo (NW Spain)

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 435:125-140 (2011) - DOI: https://doi.org/10.3354/meps09200 Byssus secretion of Mytilus galloprovincialis: effect of site at macro- and micro-geographical scales within Ría de Vigo (NW Spain) Jose M. F. Babarro1,*, Emily Carrington2 1Instituto de Investigaciones Marinas CSIC, Eduardo Cabello 6, 36208 Vigo, Spain 2Friday Harbor Laboratories, Department of Biology, University of Washington, Friday Harbor, Washington 98250, USA *Email: jbabarro@iim.csic.es ABSTRACT: The effect of the abiotic environment on byssus tenacity and associated features was investigated for Mytilus galloprovincialis in the Ría de Vigo (NW Spain). The effect of site was examined at macro-geographical (outer exposed Cabo Estay vs. inner sheltered San Simón Ensenada sites) and micro-geographical (intertidal vs. subtidal locations) scales. Site significantly influenced byssus tenacity, shape and byssus thread diameter, whereas location did not. Qualitative analysis of the byssus corroborated the importance of site; mussels inhabiting the rougher outer Ría secreted stronger and stiffer threads regardless of location and had a higher potential to form cross-links or metal chelation in the byssal collagen to gain structural integrity when needed. When mussels were transplanted between exposed and sheltered sites, asymmetrical changes were observed in tenacity, endogenous indices, byssus morphology and mechanical properties after 3 mo. Individuals transferred from the sheltered to the exposed site shifted all variables, suggesting that mussels have a plastic response to rougher environments by increasing byssus size and mechanical integrity. In contrast, mussels transplanted from the exposed to the sheltered site shifted tenacity, endogenous indices and thread length but not thread diameter nor mechanical properties. In summary, we report the highly dynamic nature of the mussel ability to modify byssus tenacity when subjected to abrupt environmental changes. Mussels have the potential to change byssus diameter and mechanical properties to increase strength in stressful abiotic conditions, and can re-allocate energy for vital structures such as gonadal and soft tissue growth in more benign environments. KEY WORDS: Mytilus galloprovincialis · Tenacity · Field · Byssus secretion · Abiotic environment · Tidal exposure · Plasticity Full text in pdf format PreviousNextCite this article as: Babarro JMF, Carrington E (2011) Byssus secretion of Mytilus galloprovincialis: effect of site at macro- and micro-geographical scales within Ría de Vigo (NW Spain). Mar Ecol Prog Ser 435:125-140. https://doi.org/10.3354/meps09200 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 435. Online publication date: August 22, 2011 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2011 Inter-Research.

Growth rates of the two reef-building species, Acropora humilis and Millepora platyphylla at Hurghada, Red Sea, Egypt

inear growth rates were measured for two species of coral namely, Acropora humilis and Millepora platyphylla in Hurghada during the period from autumn 2006 to summer 2007. In addition, the rates of recovery in man-made lesion in M. platyphylla were estimated on seasonal basis. The linear growth rates of A. humils varied significantly according to the sheltering condition, with an overall mean of 8.89 and 6.98mm/year in exposed and sheltered sites. The highest linear growth rate of A. humilis was estimated at the exposed site of Gotta Abu Ramada, being 9.17mm/year, while the lowest rate of 6.61mm/year was recorded at the sheltered site of El-Fanadir Reef. The seasonal linear growth rates of M. platyphylla were affected significantly by the sheltering condition, and non-significantly by seasons. The estimated annual growth rates of M. platyphylla at the exposed sites averaged higher value of 15.65mm/year compared to 11.29mm/year at the sheltered sites. On the seasonal level, the highest overall mean of growth rates was recorded in spring, while the lowest mean was in autumn, being 3.72 and 3.06mm/season, respectively. The rates of diametric lesions recovery of M. platyphylla varied significantly according to seasons and non-significantly according to sheltering condition. The fastest recovery was recorded in summer, while the lowest recovery was in winter. For instance, the lesions of 3847mm 2 area each, recovered completely within 6 weeks in summer, while the same lesions area were not recovered completely after 12 weeks in winter.

Sitka spruce (Picea sitchensis) forests in Atlantic Europe: changes in forest management and possible consequences for carbon sequestration

Sitka spruce (Picea sitchensis (Bong.) Carr.) was introduced in Atlantic Europe in the nineteenth century. Forests of this species are the major forest type in the United Kingdom and Ireland, with substantial areas in Norway, France and Denmark. Most forests are managed under a patch clearfelling regime on comparatively short (35–50 years) rotations. However, forest policies in a number of countries seek to increase the structural and species diversity of Sitka spruce forests: such measures are also proposed to help adapt to projected climate change and management of climate risk. Datasets from 26 experimental plots in Atlantic Europe representing existing and alternative management approaches showed high carbon stocks under current management and lower stocks in all alternatives. In addition, there was little evidence of Sitka spruce being grown successfully in long-term intimate mixture. Thinning is required to increase the diversity of Sitka spruce forests, but this can result in increased risk of wind damage, and hence reduction in carbon stocks, other than on the most sheltered sites. Such risks will be higher with the wetter soils anticipated from greater winter rainfall. Future management of Sitka spruce forests for carbon sequestration should focus both on improvement of current management (e.g. use of higher-yielding genotypes) and on developing wind-stable stands through careful thinning to act as long-term carbon stores.

Widespread occurrence of the non-indigenous ascidian Corella eumyota Traustedt, 1882 on the shores of Plymouth Sound and Estuaries Special Area of Conservation, UK

The ascidian Corella eumyota, originally from the Southern Hemisphere, was first reported in the Northern Hemisphere in Brittany, France, in 2002. Since then, it has been recorded in Spain, Ireland, the south coast of England and South Wales. Most European records to date have been from artificial habitats such as marinas. In Plymouth, England, C. eumyota was first found in two marinas in 2005 but individuals were soon also detected in small numbers on nearby shores. Shore surveys in March and August of 2008 indicated that C. eumyota has established reproductive populations on natural and semi-natural shores of Plymouth Sound and the adjacent coastline, largely restricted to relatively sheltered sites in the lower reaches of estuaries. At these sites it is generally the most abundant non-colonial ascidian. The species clearly has the capacity to become a significant component of the biota of sheltered shores in the Northern Hemisphere.

Polychaetes and oligochaetes associated with intertidal rocky shores in a semi-enclosed industrial and urban embayment, with the description of two new species

The species composition and relative abundance of the annelid benthic macrofauna (Polychaeta and Oligochaeta) inhabiting the rocky intertidal zone of the ria of Ferrol (Galicia, NW Spain) were studied during field collections, from 2000 to 2002. A total of 14,619 specimens (11,585 polychaetes belonging to 76 species and 24 families and 3,034 oligochaetes belonging to 18 species and two families) were collected from 98 quantitative samples taken from 13 sampling sites. The general spatial distribution of the annelid fauna reflects an increase of the diversity from the inner to the outer part of the ria. The general patterns found in the annelid composition suggest that the assemblages were dominated by oligochaetes in the inner sheltered sampling sites and polychaetes in the outer more exposed sites. Several faunistical and taxonomical remarks on selected species are presented. Two new species of oligochaetes are described: Coralliodrilus artabrensis sp. n. and Pirodrilus fungithecatus sp. n. (Naididae, Phallodrilinae). A new biological index, based on the oligochaete/polychaete ratio (O/P), is proposed as tool to evaluate environmental quality and to monitor future changes in the environment.

Increases in the abundance of the invasive barnacle Austrominius modestus on the Isle of Cumbrae, Scotland

The distribution and abundance of the Australasian barnacle Austrominius modestus around the Isle of Cumbrae, Scotland, were examined in October 2007. The species was found at all of the nineteen sites examined, which included highly exposed to highly sheltered sites. Its abundance varied from common to occasional. Over fifty years after its initial appearance as a single specimen (1954), Austrominius now appears to be well established on the island. Factors that may have influenced its spread and establishment are described, however, at this stage the relative importance of these cannot be determined. Consequently, further research is planned here, to collect quantitative data on the abundance of Austrominius and the other barnacle species that occur intertidally and how their relative abundances vary both within and between shores.

Revisiting the meiofauna paradox: dispersal and colonization of nematodes and other meiofaunal organisms in low- and high-energy environments

How do small, benthic meiofaunal organisms become cosmopolitan over large geographic ranges? Abiotic forces including oceanic currents are believed to be of key importance in aiding marine meiofaunal dispersal. We investigated the effect of distance from substrate and site exposure on meiofaunal colonization and transport in the water column. First, we tested how distance from substrate and sediment grain size affected colonization of azoic sediments by meiofauna in a sheltered inlet. Nematodes, crustacean nauplii and small amphipods colonized distant sediment cages (3 m above bottom) as quickly and abundantly as cages closer to the ocean floor. Some of the 30 recorded genera of nematodes predominated in one height treatment whereas abundance of others was not related to distance from the substrate. Polychaetes and harpacticoid copepods colonized near-benthic cages more rapidly and abundantly than those farther away suggesting active dispersal. Nematodes, harpacticoids and polychaetes were more abundant in fine than in coarse sediments, while nauplii and amphipods did not differ in abundance between sediment types. In part two of this study, we surveyed occurrence of meiofauna in the water column at several sheltered and exposed sites using plankton nets towed at fixed distances from 0.5 to 6.5 m above the ocean floor. Because oceanic currents increase sediment suspension and transport, we expected to see more meiofauna in samples collected from exposed than from sheltered sites. However, with the exception of polychaetes, which were more abundant in the water column of sheltered sites, there was no difference in meiofaunal abundances between the two exposure classes. Meiofauna, including the 14 identified nematode genera, were collected in greatest numbers nearer to the ocean floor and dwindled further up in the water column. The presence of meiofauna high in the water column of even the most sheltered sites combined with the quick and abundant colonization of distant, sheltered sediment cages suggests that even very weak currents are sufficient to suspend and transport these animals or that many meiofaunal taxa are capable of active dispersal into the water column.

Modelling wave-induced disturbance in highly biodiverse marine macroalgal communities: support for the intermediate disturbance hypothesis

As biodiversity declines globally, it is becoming increasingly important to understand the processes that create and maintain biodiverse communities. We examined whether the extraordinarily high species diversity of macroalgal communities in shallow coastal waters off south-west Western Australia is related to wave-induced physical disturbance. We used the numerical wave model SWAN to estimate the hydrodynamic forces generated by waves in bathymetrically complex coastal reefs. Oscillatory water motion at the seabed during extreme wave events was used as an index of physical disturbance in macroalgal communities. There was a significant curvilinear relationship between species diversity and disturbance index, consistent with the intermediate disturbance hypothesis (IDH). Diversity was lower at exposed offshore sites where disturbance is likely to be highest and at very sheltered sites with the least disturbance. Our results match those from some other highly diverse habitats, including rainforests, grasslands and coral reefs in which patchy, stochastic disturbance regimes have been hypothesised to prevent the development of homogeneous climax communities, promoting spatiotemporal heterogeneity and increasing total system diversity. Our results represent important evidence in support of a role for the IDH in driving diversity in marine plant communities.

DISTRIBUITION OF CRUSTOSE CORALLINE ALGAE (CORALLINALES, RHODOPHYTA) IN THE ABROLHOS REEFS, BAHIA, BRAZIL

ABSTRACT The crustose coralline algae have an important structural role in coral reef crests, as observed for some Atlantic reefs. In this work the distribution and abundance of crustose coralline algae and their relation to other benthic reef organisms were described for the Abrolhos Archipelago. The quantification of sessile organisms was made by SCUBA diving along replicated transect lines in different habitats and sites. Anovas were performed to test differences on algae abundance among sites and habitats. Coralline crusts did not show significant differences on abundance among sites (Anova, p&gt;0,05), neither other benthic organisms (Anovas, p=0,634 invertebrates, p=0,767 filamentous algae, p=0,581 foliose algae, p=0,070 leathery algae and p=0,616 non calcareous crusts). Invertebrates and filamentous algae were the most abundant organisms on all sites and most habitats, contrasting with the low cover of coralline algae. In sheltered sites and on reef base it was observed a trend for an increase of fleshy foliose algae and leathery algae, contrasting with wave exposed sites. The distribution of coralline growth forms was characterized by a higher abundance of flat in relation to branched thalli. Branched coralline crusts are apparently more abundant within cryptic reef areas, not necessarily because of light limitation, but probably due to less herbivore pressure.

Dominant environmental factors in wetland plant communities invaded by Phragmites australis in East Harbor, Ohio, USA

Elevation, standing crop, disturbance and soil fertility often emerge from studies of freshwater plant communities as the dominant environmental factors determining both species richness and species composition. Few studies in North America have investigated the relationship between these factors and species abundance (standing crop) and species composition in the context of invasion by Phragmites australis. This study explores the influence of key abiotic and biotic variables on species abundance and composition across three Lake Erie wetlands differing in hydrology and Phragmites abundance in East Harbor, Ohio, USA. Standing crop for 92 species was related to standard sediment analyses, wave exposure, distance to shoreline, elevation, light interference, species density, and Phragmites standing crop in each of 95 1 × 1 m quadrats by using canonical correspondence analysis (CCA). Elevation (Axis I) and Phragmites standing␣crop-soil fertility (Axis II) explained 35.7 and 26.2%, respectively, of the variation in the species–environment relationships. Wave exposure was not a primary component of the first four canonical axes. Axis I was instrumental in describing species composition, separating wet meadow species from marsh species. Axis II was inversely related to species density for both wet meadow and marsh species. These findings generally support prevailing models describing the distribution of wetland plants along environmental gradients. Two discrepancies were noted, however: (1) species density was highest in the most sheltered sites and (2) wave exposure was directly associated with Phragmites standing crop-soil fertility gradient. The structural integrity of Phragmites stems, topographic heterogeneity and differential responses to anthropogenic disturbance may contribute to departure from prevailing multivariate models. This information has direct implications for local and regional wetland managers.

Patterns of sponge distribution in Cagarras Archipelago, Rio de Janeiro, Brazil

The structure and distribution of the sponge community in five sites and four habitats in Cagarras Archipelago, Rio de Janeiro, Brazil, are described. The archipelago has three major islands (Cagarra, Palmas, and Comprida), and four islets. Qualitative samples were taken by SCUBA diving in the three islands and in two islets, and quantitative samples were taken in Palmas Island only. Cluster analysis using Jaccard's coefficient on qualitative data grouped the two islets (Cagarra Bank and Cagarra Islet), which are more exposed to wave action, and the three islands formed a group of relatively sheltered sites. Cluster analysis using Bray–Curtis coefficient on quantitative data from different habitats in Palmas Island allowed distinction of three groups of samples: overhangs, shallow horizontal surfaces (6 m depth), and vertical walls plus deeper horizontal surfaces (17 m depth). Sponge abundance was greater in overhangs (61·2 ind m−2), which were dominated by Protosuberites sp. and Clathrina conifera. Abundance was reduced in vertical walls (31·1 ind m−2) and deep horizontal surfaces (16·8 ind m−2). Pachychalina sp. dominated the deep horizontal surfaces and Clathrina conifera was dominant in overhangs. Values of Shannon's diversity in overhangs, vertical walls (both with H′=2·1 bits ind−1) and deep horizontal surfaces (H′=1·7 bits ind−1) were moderate and similar, whereas in shallow horizontal surfaces the sponges were both less diverse (H′=0·37) and less abundant (8·5 ind m−2). Shallow horizontal surfaces were dominated by Hymeniacidon heliophila. The reduced species richness of the sponge community in Cagarras Archipelago when compared with other sites in Brazil and elsewhere is probably due in part to the pollution from the city of Rio de Janeiro. Wave action appears to reduce the number of sponge species at a local scale, whereas substrate inclination affects more strongly the species composition and abundance than the diversity of sponges.