Algae-associated marine molluscs in the Azores

The raolluscan fauna of a special habitat, the high intertidal algal turf, was studied at four stations on the island of Sao Miguel, Azores. The number of species found ranged from 13 to 23. However, a small group of only six species (the bivalve Lasaea adansoni and the gastropods Pisinna punctulum, Omalogyra atomus, Fossarus ambiguus, Skeneopsis planorbis and Alvania postrema) accounted for more than 80% of all the specimens collected. Mollusc density reached values of 20000 specimens per 100 g algal dry weight. The abundance and number of species of molluscs was comparable with those reported for algal zones lower on the Azorean shores.
Wave exposure and seasonality effects were found to be small, presumably because of the relatively mild abiotic conditions and the protective role of the turf. The algal substrata influenced the phytal molluscan community in two ways. First, the abundance of molluscs was significantly correlated with algal dry weight. Secondly, molluscan abundance and diversity were influenced by the algal composition of the turf. A rich algal composition, with several species of branched fleshy and coralline algae, was associated with a rich molluscan fauna. The dominance of coralline algae resulted in a abundant but species-poor fauna, while an almost monospecific turf of Gigartina was poor in both species and number of molluscan fauna.     

Ecology and dynamics of two intertidal algal communities on the littoral of the island of São Miguel (Azores)

The intertidal benthic algal communities of two sites located on opposite coasts of São Miguel Island (Azores), were studied over a 2-year period (September 1993–September 1995). At both sites (São Roque on the south coast and São Vicente on the north), the littoral region was surveyed from the upper intertidal down to the sublittoral fringe. The survey revealed five distinct zones, with a variable degree of overlapping. The two upper zones were characterized by animals (littorinids and barnacles, respectively). Lower down, algal communities formed three distinct zones: an upper Fucus spiralis/Gelidium microdon association, a more extensive turf zone, and a belt featuring erect or frondose algae. Upper in the eulittoral, the turf was mainly monospecific, and dominated by Caulacanthus ustulatus. The lower eulittoral turf was dominated by articulated coralline algae, the associated species differing between the two sites studied. Mainly erect algae (Pterocladiella, Asparagopsis, etc.) occurred furthest down the shore and extended into the nearby shallow sublittoral. Two intertidal communities were studied at each locality: the upper eulittoral (Caulacanthus turf in São Roque and the Fucus spiralis/Gelidium microdon association at São Vicente), and the lower eulittoral (the coralline turf). The lower littoral communities had a higher algal diversity. A general pattern was observed in the seasonal variation of biomass: the lower levels exhibited the higher values in late summer/early autumn, the period in which the upper levels had the lowest standing crops. Physical factors are proposed to account for this. No significant inter-annual variations could be detected, indicating relatively stable communities, at least on a short-term basis.     

Macroalgal species diversity and biomass of subtidal communities of São Miguel (Azores)

The benthic algal communities of two subtidal sites, located on opposite coasts of S?o Miguel Island (S?o Roque in the south and S?o Vicente on the north coast), were studied over a 2 year period (September 1993–September 1995). At both sites the sublittoral region was surveyed from low-tide level down to a depth of 15 m. Qualitative and quantitative changes are described. A depth-related gradient in species diversity and biomass was found at both localities. In general, red algae such as corallines and Pterocladiella capillacea predominated in the shallow sublittoral (5 m) while brown algae such as Zonaria and Stypocaulon were more abundant at 15 m. Multivariate analyses emphasized the existence at each study site of two communities (5 and 15 m depth), separated by a large transition zone. The 15 m community on the south coast site showed the largest number of species (52), whereas the lowest diversity (30 species) also occurred at this site in the 5 m community. A clear seasonal pattern of biomass change could be discerned only at S?o Vicente where the highest biomass was recorded in spring/summer. No major inter-annual variations could be detected, indicating relatively stable communities at least on a short-term basis. Received in revised form: 28 March 2001 Electronic Publication     

Temporal comparison of the composition and zonation of rocky intertidal organisms at Cocos Island National Park, Pacific, Costa Rica

Several biological and physical factors change the rocky shore communities. The desiccation time and the tolerance of the intertidal species produce the vertical zonation. In many studies around the world, a temporal change in this zonation is presented.In Costa Rica, only studies that include temporal trends were carried out in Punta Mala and Montezuma, Pacific coast in 80's. The rocky intertidal of the Cocos Island National Park, Costa Rica were surveyed photographically. The Chatham bay was sampled in three expeditions (January 2007, October 2007 and April 2008). Photos corresponding to 25x25cm quadrats were taken with the goal to determine diversity and composition differences in rocky shore organisms between sampling dates. The Wafer bay was sampled in January and October 2007. The intertidal of Chatham consists of basaltic rock, while Wafer has basaltic and ignimbrite boulders. The main difference between sites were the higher algae cover (erect-frondose forms) and number of organism bands at Chatham bay. Temporal change was not found in the total cover of sessile fauna and autotrophs. The barnacle Tetraclita stalactifera, that occurs above the algal fringe (lower intertidal), was the invertebrate with the highest coverage. The mobile fauna biodiversity presented no significant trend between sampled months. However, the identity of species, their cover and their abundance showed a moderate temporal change. In October 2007, when the sea surface temperature was 23 degrees C the infralittoral zone had an increase in green algae cover. The red algae (crust and erect-frondose forms) were dominant in January and April. The pulmonate limpet, Siphonaria gigas and a bacterial biofilm at mid littoral showed a negative association. The snails of the high littoral and the supralittoral zone showed a temporal change in their abundance, but with contrasting patterns between sites. The temporal variation in the assemblages increased from the supralittoral to the infralittoral possibly due to changes in the water temperature and climatic conditions, that could influence the intertidal zone during the high and low tide, respectively.     

158 Algal Turf Composition at Two Coastal Locations on the Island Of Hawai'i

Algal turfs, or mats of interwoven multispecific algal 1–3 cm in height, play an important role in the reef community in Hawai'i, and yet they are often overlooked. Two sites on opposite coasts of the island (Richardson's Beach Park and Puako) were sampled from September 2000 to July 2002. The samples from quadrats along transect lines were analyzed to find percent abundance of each species. Specimens were examined microscopically to generate a species list. Over 50 different species of algae were identified, and red algae (Rhodophyta) dominated the samples at both sites. Several new records for the island of Hawai'i were found. Algal turf species diversity (H') varied between sites and among sampling dates. The most abundant species showed aggregated or patchy spatial patterns in the turf.     

Territorial behavior of threespot damselfish (Eupomacentrus planifrons) increases reef algal biomass and productivity

Synopsis Algal growth and damselfish (Eupomacentrus planifrons) territories were studied in two reef habitats at Discovery Bay, Jamaica. Damselfish territories were contiguous in the reef flat (0 to 2.5 m), where the algal composition and biomass varied from territory to territory. In contrast, on the lower reef terrace (22 m), damselfish territories were often spatially segregated. While the algal composition of the territories was more uniform on the reef terrace, the total algal biomass was lower than in the territories on the reef flat. Damselfish are largely herbivorous, and they defend their territories against most intruding fish, including a number of herbivorous species. Areas of the reef terrace outside of damselfish territories were heavily grazed by herbivorous fishes and contained only small quantities of non-crustose algae.The reef terrace territories were characterized by a multispecific turf of algae (greens, blue-greens, and reds) covering the Acropora cervicornis framework and by the leafy, brown alga, Lobophora variegata. A rapid reduction in the biomass of brown algae and filamentous algae was noted when damselfish were permanently removed from their territories. Only calcified, encrusting algae — plants apparently somewhat undesirable as fish food sources — would be common on the terrace zone of this reef if damselfish territories were absent. Damselfish territoriality may significantly influence the dynamics of some reefs by increasing the biomass of the algal turf thereby increasing; reef productivity. Since blue-green algae, potential nitrogen fixers, occur in these algal turfs, the fish may also be indirectly affecting reef nutrition.     

Hyperspectral and Physiological Analyses of Coral-Algal Interactions

Space limitation leads to competition between benthic, sessile organisms on coral reefs. As a primary example, reef-building corals are in direct contact with each other and many different species and functional groups of algae. Here we characterize interactions between three coral genera and three algal functional groups using a combination of hyperspectral imaging and oxygen microprofiling. We also performed in situ interaction transects to quantify the relative occurrence of these interaction on coral reefs. These studies were conducted in the Southern Line Islands, home to some of the most remote and near-pristine reefs in the world. Our goal was to determine if different types of coral-coral and coral-algal interactions were characterized by unique fine-scale physiological signatures. This is the first report using hyperspectral imaging for characterization of marine benthic organisms at the micron scale and proved to be a valuable tool for discriminating among different photosynthetic organisms. Consistent patterns emerged in physiology across different types of competitive interactions. In cases where corals were in direct contact with turf or macroalgae, there was a zone of hypoxia and altered pigmentation on the coral. In contrast, interaction zones between corals and crustose coralline algae (CCA) were not hypoxic and the coral tissue was consistent across the colony. Our results suggest that at least two main characteristic coral interaction phenotypes exist: 1) hypoxia and coral tissue disruption, seen with interactions between corals and fleshy turf and/or some species of macroalgae, and 2) no hypoxia or tissue disruption, seen with interactions between corals and some species of CCA. Hyperspectral imaging in combination with oxygen profiling provided useful information on competitive interactions between benthic reef organisms, and demonstrated that some turf and fleshy macroalgae can be a constant source of stress for corals, while CCA are not.     

Algae, macrofaunal assemblages and temperature: a quantitative approach to intertidal ecosystems of Iceland

Algae and the associated macrofauna in two Icelandic intertidal ecosystems under cold and warm influence, respectively, were studied with respect to algae-macrofauna relationships and a possible effect of temperature on community structure. Two sites in Iceland were selected, Sandgerdi ligthhouse (64°8′N 22°40′W) on the southwestern coast, and Grimsey Island (66°33′N 18°04′W), in the north, on the Arctic Circle, where sea temperature is considerably lower (5° approximately). The biomass of algae and the number of species of algae and macrofauna were higher in Sandgerdi than in Grimsey, and the patterns of diversity, evenness, biomass and abundance also differed between the sites. In the intertidal zone of Sandgerdi, a total of 28 species of algae and 45 species of macrofauna were identified whereas only 16 algal species and 27 macrofaunal species were found in Grimsey. Canonical correspondence analysis (CCA) using algal biomass as the environmental variable were conducted, and revealed significant relationships between algae composition and the associated macrofauna; some macrofauna taxa showed specific trophic or refuge relationships with algal species. According to the CCA, Corallina officinalis showed the highest correlation with macrofaunal assemblages in both study sites. However, correlations between macrofauna and other algae differed between Grimsey and Sandgerdi. The present study, together with additional observations in Greenland waters, shows a general decrease of species richness and diversity towards the north which may primarily be due to the temperature regime.     

159 Incertae Sedis No More: The Phylogenetic Affinity of Helicosporidia

Algal turfs, or mats of interwoven multispecific algal 1–3 cm in height, play an important role in the reef community in Hawai'i, and yet they are often overlooked. Two sites on opposite coasts of the island (Richardson's Beach Park and Puako) were sampled from September 2000 to July 2002. The samples from quadrats along transect lines were analyzed to find percent abundance of each species. Specimens were examined microscopically to generate a species list. Over 50 different species of algae were identified, and red algae (Rhodophyta) dominated the samples at both sites. Several new records for the island of Hawai'i were found. Algal turf species diversity (H') varied between sites and among sampling dates. The most abundant species showed aggregated or patchy spatial patterns in the turf.     

The zoogeography of algae-associated peracarids along the Pacific coast of Chile

Abstract Aim To describe the zoogeography of the algae‐associated peracarid crustaceans from exposed rocky shores along the SE‐Pacific. Location Chile, 18° S to 42° S. Methods A standardized sampling programme was used at all sites. Samples of macroalgae were taken at twenty sites distributed along the entire study area. Quantitative samples (n = 6 replicates of 8 cm^?2 surface area each) of calcareous and non‐calcareous red algae were taken in the low intertidal, preserved immediately in 4%‐formalin and washed over a 0.2‐mm mesh before sorting. All peracarid individuals were sorted, identified to the species level and then categorized in separate functional groups according to their feeding habits. Graphical representations of species replacement within each functional group along the latitudinal gradient are provided. A classification analysis employing the unweighted paired group method using arithmetic average (UPGMA) was conducted in order to reveal the main zoogeographical zones. Results A total of forty epifaunal peracarid species was found. A gradual replacement of species within different functional groups (grazing and suspension‐feeding species) was observed in the central region (c. 26° S?37° S). In this central region, species with northern and those with southern distribution overlapped, while other species were only found here, resulting in high species richness. The number of species/site/algal species in the northern (north of c. 25.5° S) and southern region (south of c. 38.5° S) was considerably lower than in the central region. The distribution of most grazing peracarids showed a more continuous pattern than that of suspension‐feeding amphipods. The distribution of the remaining species (predators, scavengers, deposit‐feeders, unknowns) was scattered along the examined sites. The cluster analysis for the epifaunal peracarid assemblage confirmed the separation of a northern and southern zone connected by a central (transitional) zone between c. 26° S and c. 37° S. Similar zonation patterns have been found by most other studies on the zoogeography of the Chilean coast, although little agreement exists about the exact limits of this transitional zone. It is discussed that the distribution limits of algae‐associated peracarids (and other macroinvertebrates) – particularly in the transitional zone – may show interannual variations as a result of varying oceanographic conditions. The large affinity of the algae‐associated peracarid fauna from the central and southern Chilean coast to those of other regions indicates that dispersal may be facilitated by rafting with floating algae transported in the Antarctic Circumpolar Current. Main conclusions The zoogeographical analysis of algae‐associated peracarids confirms the existence of a northern and a southern zone connected by an extensive transitional zone. General biology, habitat use and the abundant presence of dispersal vectors such as floating macroalgae may affect the zoogeography of species living in transitional zones with strong interannual variations in current regimes. In these areas, species associated with substrata of high dispersal potential may show different distribution patterns than species inhabiting other substrata.     

Changes in the species composition of benthic macroalgal communities of the upper subtidal zone on a coral reef in Sanya Bay (Hainan Island, China) during 2009–2012

Investigations of macroalgae were carried out on a coral reef at the Luhuitou Peninsula in Sanya Bay (Hainan Island, China) in the upper subtidal zone at a depth of 0.5 to 4 m during the dry season (in April 2009 and 2012). In total, 130 species, varieties, and forms of marine macroalgae were found: 71 (54%) Rhodophyta, 33 (25%) Chlorophyta, and 26 (21%) Phaeophyceae. In terms of the number of species and the floristic composition of algae in the communities, the reef benthic flora in the subtidal zone of Sanya Bay, which is polluted by municipal waste waters and aquaculture wastes, was close to the flora of Indo-Pacific coral reefs situated in areas with low pollution. In 2009 and 2012, the algal turf communities differed both in the algal species diversity and in the composition of dominant species. These differences might be due to an annual periodicity of changes in vegetation: algal turf patches are detached from the hard substrate and a new algal community is formed at this location.     

The effects of grazing on the distribution and composition of low-shore algal communities on the central coast of Portugal and on the southern coast of Britain

A red algal turf is often found just below the barnacle/limpet zone of many European shores, especially on steep shores of moderate exposure. The hypothesis that grazing by limpets determines the upper limit of distribution of this red algal turf was tested on moderately exposed shores in Portugal and Britain. We also aimed to assess whether the grazing effect is modified at various spatial scales. Grazers were excluded by fences, with half-fenced and unfenced controls. Exclusion plots were rapidly colonised by green ephemeral algae in the months immediately after the beginning of the experiment (summer); these algae were later replaced by perennial algae. The percentage cover of turf-forming macroalgae showed a significant increase at both locations. The upper limit of distribution extended more than 50 cm on most of the shores studied. In contrast, control and half-fenced plots remained devoid of algae. After 2 years, ungrazed plots were mainly colonised by a red algal turf (e.g. Caulacanthus ustulatus, Gelidium spp., Laurencia pinnatifida) in Portugal, while canopy cover (Fucus serratus and Himanthalia elongata) dominated in Britain in marked contrast to the grazed plots. Physical factors acting at both local and geographical scales may explain these differences. However, although physical factors probably have an important influence on the identity, size and abundance of sublittoral fringe macroalgae, grazers play a major role in directly setting their upper limits. The effect of grazing by limpets was not consistent for all of the morphological algal groups and spatial scales considered in the present study. The effect of grazing on the cover of turf algae varied between Portugal and Britain (location scale), while effects on ephemeral and canopy algal cover varied at the shore scale within location.     

Algal fouling of underwater structures at lobster farms in Nha Trang Bay (Vietnam)

The species composition and structure of algal fouling communities on the underwater artificial substrates at lobster farms in Nha Trang Bay (Vietnam) were studied for the first time. In total, 126 taxa (species and forms) of macroalgae (24% green, 16% brown, and 60% red), as well as eight species of cyanobacteria, were found. Depending on the area and quality of the substrate, fouling algae form polydominant turf communities, mono- and bidominant communities of crustose algae, or no specific communities. The flora of macroalgal fouling at lobster farms in Nha Trang Bay was similar in terms of its diversity and species composition to that of coral reefs in areas of the Indo-Pacific with a low level of pollution. This similarity might be due to the diversity and cleanness of the substrates (the absence of sediment on the surface of the underwater structures).     

Different algal symbionts explain the vertical distribution of dominant reef corals in the eastern Pacific

Symbiotic reef corals occupy the entire photic zone; however, most species have distinct zonation patterns within the light intensity gradient. It is hypothesized that the presence of specific symbionts adapted to different light regimes may determine the vertical distribution of particular hosts. We have tested this hypothesis by genetic and in situ physiological analyses of the algal populations occupying two dominant eastern Pacific corals, over their vertical distribution in the Gulf of California. Our findings indicate that each coral species hosts a distinct algal taxon adapted to a particular light regime. The differential use of light by specific symbiotic dinoflagellates constitutes an important axis for niche diversification and is sufficient to explain the vertical distribution patterns of these two coral species.     

Role of colonization in spatio-temporal patchiness of microgastropods in coralline turf habitat

The ability of benthic macrofauna to disperse and colonize new habitats throughout their life may contribute substantially to small-scale patchiness in abundances in different habitats. Microgastropods in coralline turf on rocky shores in Australia are very patchy in abundance at different spatio-temporal scales. They therefore represent an ideal assemblage for testing hypotheses about processes of colonization. Patterns and rates of colonization of 10 species of microgastropods were investigated in one intertidal habitat (coralline turf) in Botany Bay, New South Wales, Australia, using artificial substrata, which are considered to be a good mimic of natural coralline turfs. The experiment was designed to test the hypotheses that (1) patterns (abundance of colonizing individuals) and mode (juveniles vs. adults) of colonization depends on the proximity of a patch to a potential source of dispersing colonists (i.e. patch of natural coralline turf), (2) different species show different rates of colonization, and (3) patterns of succession are not repeatable among different patches of natural algae. Seven different plots (natural patches of coralline turf) were randomly chosen in the area of study. Artificial units (called patches) were placed at different distances around each plot (within the plot and 0, 50 or 100 cm away from the edge). Samples were collected 6, 13, and 27 days after the experiment started. Colonization was rapid (i.e. within 6 days) for most species. Pattern (number of individuals) and mode of colonization (adults vs. juveniles) varied among algal plots. Most species responded differently across patches causing no consistent patterns of colonization. Furthermore, patterns of colonization of artificial units were not always synchronous with, or in the same direction as, changes in abundances in the nearest algal plots, which themselves showed no consistent spatio-temporal pattern.     

Sea surface microlayer and elemental composition in phaeo‐, chloro‐, and rhodophytes in winter and spring

Trace metal or rare earth element (REE) content of marine macroalgae are underexamined and there is a great need for further understanding since macroalgae are used for food and may also be bioindicators of environmental changes. This study, by using high resolution inductive coupled plasma spectrometer in a clean laboratory (class 1000), investigates the trace metal and REE concentrations and composition in the youngest tissue of various species within three algal classes in the Trondheimsfjord, Norway, comprising phaeo‐, chloro‐, and rhodophytes in winter (February) and Spring (May) 2013, with the main focus on phaeophytes. The macroalgae were found in a clear zonation pattern as a function of depth. A significant difference in element concentration and composition was found between the six phaeophyte species along with a significant difference between winter and spring tissue. A zonation depth trend in algal tissue element concentration was also found for the phaeophytes, where the algal species located in both extreme ends (upper vs. lower littoral zone) obtained a lower element concentration than the algae located in the middle part of the littoral zone. This trend seems to result from different algal contact with the metal‐rich sea surface microlayer. The chlorophytes had 5–27 times higher concentration of REE and lead (Pb) than the two other algal classes. Results indicate that the rhodo‐ and chlorophytes are better accumulators than the phaeophytes for several trace metals and REE.     

High rhenium enrichment in brown algae: a biological sink of rhenium in the sea?

Twenty-one species of seaweed from the California coast were analyzed for rhenium. For the first time, high enrichment (thousandfolds) of rhenium relative to seawater was found in brown algae, but not in green or red algae. Brown algae was suggested as a biological sink of rhenium in the sea and the analogous behavior of technetium to rhenium was found in marine algae. Preliminary incubation experiments with a common brown alga (Pelvetia fastigiata) showed that algal surface is not a major accumulating locus of rhenium.     

Living on a volcano's edge: genetic isolation of an extremophile terrestrial metazoan

Communities of organisms inhabiting extreme terrestrial environments provide a unique opportunity to study evolutionary forces that drive population structure and genetic diversity under the combined challenges posed by multiple geogenic stressors. High abundance of an invasive pantropical earthworm (and the absence of indigenous lumbricid species) in the Furnas geothermal field (Sao Miguel Island, Azores) indicates its remarkable tolerance to high soil temperature, exceptionally high carbon dioxide and low oxygen levels, and elevated metal bioavailability, conditions which are lethal for the majority of terrestrial metazoans. Mitochondrial and nuclear markers were used to analyze the relationship between populations living inside and outside the geothermal field. Results showed that Pontoscolex corethrurus (Annelida, Oligochaeta, Glossoscolecidae) to be a genetically heterogeneous complex within the Sao Miguel landscape and is probably differentiated into cryptic species. The population exposed to the hostile soil conditions within the volcanic caldera possesses the lowest within-population mitochondrial diversity but an unexpectedly high degree of nuclear variability with several loci evidencing positive selection, parameters indicative of a genetically unique population only distantly related to conspecifics living outside the caldera. In conclusion, P. corethrurus inhabiting active volcanic soil is a discrete extremophile population that has evolved by tolerating a mixture of non-anthropogenic chemical and physical stressors.     

Small-scale spatial variability in intertidal and subtidal turfing algal assemblages and the temporal generality of these patterns

Spatial and temporal variation in patterns of distribution and abundance of algal assemblages is large and often occurs at extremely small spatial and temporal scales. Despite this, few studies investigate interactions between these scales, that is, how patterns of spatial variation change through time. This study investigated a number of scales of spatial variation (from tens of centimetres to kilometres) in assemblages of intertidal and subtidal turfing algae. Significant differences were found in the composition and abundances of species in assemblages of turf at all spatial scales tested. Much of the variation among assemblages could, however, be explained at the scale of quadrats (tens of centimetres apart) (27±1.4 (SE)% of dissimilarity) with an additional 7±1.2% explained at the scale of sites (tens of metres apart) and 10±1.5% at the scale of locations (kilometres apart). Although the greatest dissimilarity in assemblages occurred at the scale of habitats, this accounted for a relatively small proportion of the overall variation in assemblages. These patterns were consistent through time, that is, at each sampling time the spatial scale explaining the greatest proportion of variation in assemblages was replicate quadrats separated by tens of centimetres. These patterns appear to be due to small-scale variation in patterns of distribution and abundances of the individual species that comprise turfing algal assemblages. The results of this experiment suggest that large scale processes have less effect on patterns of variability of algal assemblages than those occurring on relatively smaller spatial scales and that small-scale spatial variation should not be considered as simply “noise”.     

Impacts of a ‘black tide’ harmful algal bloom on rocky-shore intertidal communities on the West Coast of South Africa

Algal blooms commonly occur along the South African west coast. In March 1994 a dense bloom developed within St Helena Bay. Its subsequent decay caused near-shore hypoxia and elevated hydrogen sulphide levels, leading to it being termed a ‘black tide’. The bloom caused immediate massive intertidal mortalities (95% reduction of biomass), significant changes in community structure, and declines in richness and diversity. Only four taxa were not diminished: ephemeral algae, the gastropod Afrolittorina knysnaensis, the anemone Bunodactis reynaudi and the false limpet Siphonaria capensis. This limpet species subsequently increased at impacted sites relative to controls, probably reflecting reduced competition from other grazers. Ephemeral algae flourished during early recolonisation while grazers were depleted, but declined as grazers re-established. Manipulative experiments demonstrated that grazers do have this capability. Perennial algae also flourished, but lagged behind ephemerals, possibly contributing to their decline. Predators took longest to recover. Differences in the responses of species reflect differing tolerances, zonation patterns and biological interactions. Communities at control sites remained unchanged over the four-year study, and those exposed to a low intensity of the bloom were little affected, but communities exposed to its full intensity failed to recover fully within four years. Increasing frequency of harmful algal blooms along the west coast of South Africa could, therefore, significantly alter rocky-shore communities if intervals between bloom events become shorter than recovery times.