Factors affecting fish diversity on a temperate reef: the fish assemblage of Palos Verdes Point, 1974–1981

Synopsis We conducted underwater fish assemblage surveys, benthic quinaldine sampling, and ichthyoplankton collections over high and low relief reefs at Palos Verdes Point, California from 1974 through 1981. Seventy-three species (adults and larvae) were collected or observed at Palos Verdes. Of the 24 most abundant species, 8 showed significant abundance trends correlated with changes in sea surface temperatures; four increasing, and four decreasing. Two taxa occurred predominantly in the kelp canopy, while seven others were distributed at least 20% of the time between the canopy and the bottom. There was little significant change in the Palos Verdes benthic fish assemblage with development of the kelp bed. Only the kelp bass, Paralabrax clathratus, showed a significant increase in abundance that correlated with the kelp bed formation. Similarly, we did not note an increase in juvenile fish during this period. In general, we suggest that the presence or absence of kelp has little effect on the abundance of most fish species in a high relief environment. Analysis of our data and that of other studies indicate that kelp bed fish assemblages within the Southern California Bight vary in a south-north direction. The Palos Verdes Point kelp bed appears to be more productive than those nearer the limit of the Bight, but was consistently lower in both fish abundance and diversity then the nearby breakwater at King Harbor. This difference has been maintained even though changes in the species structure at King Harbor has altered sufficiently since 1976 for the two formerly distinct assemblages to be significantly concordant.     

Habitat characteristics can influence fish assemblages in high latitude kelp forests

Kelp forests are patchy fish-associated habitats, which can vary greatly in their size, foundation species, and several physical habitat attributes. The structure of fish assemblages can vary with these characteristics and with the location of the assemblage within the forest, i.e. edges versus interiors. This study quantified the biological and physical heterogeneity within different sized kelp forests and identified which factors are important in structuring the associated fish assemblages. Fish and habitat surveys were conducted at the edge and interiors of ten kelp forests of varying sizes in Kachemak Bay, south-central Alaska. Fish assemblage structure was not correlated with the species composition of surface canopy forming foundation kelps (Nereocystis leutkeana and Eualaria fistulosa) or with kelp forest size. Instead, it correlated with the abundances of two understory foundation kelps (Agarum clathratum and Saccharina latissima), substratum rugosity, and water depth. Together these benthic attributes explained 53.6 % of the fish assemblage variability. Additionally, significantly different fish assemblages were found at edge compared to interior locations with the relative abundance of seven species (Artedius fenestralis, Ammodytes hexapterus, Blepsias cirrhosis, Gadus macrocephalus, Hexagrammos stelleri, Pholis laeta, and Sebastes melanops) explaining 91.4 % of the variability. This study highlights the importance of habitat characteristics such as understory foundation species, substratum rugosity, water depth and location within a patch on the variability of fish assemblages in high latitude kelp forests.     

Community structure of fishes attracted to shallow water fish aggregation devices off South Carolina,U.S.A.

Synopsis Twenty-two fish aggregation devices were deployed in 14 m of water off South Carolina. Species composition and abundance were determined by diver visual census on eight occasions from May through November, 1985. A total of 21 families and 36 species of fishes was observed at 121 stations. Pelagic fishes dominated the fauna with a 99.3% relative abundance, and Decapterus punctatus accounted for 97.6% of the individuals. Caranx crysos, Diplectrum formosum, Decapterus punctatus, Centropristis striata and Monacanthus hispidus were the most frequent species. Total fish abundance, number of species and abundance of four of the six most common species were significantly affected by season. Hurricane activity may have caused a significant drop in pelagic fish abundance at the FADs in July. No significant correlations among species abundances were found after removal of season and FAD type effects. Spatial zonation and seasonal occurrence patterns suggest some competition among pelagic fishes. Several factors that regulate FAD faunal abundance and composition are hypothesized, including: juvenile fish availability, availability of shelter, availability of adequate food resources, interspecific and intraspecific competition, severe sea conditions, and sporadic intrusions of large predatory fishes. It is hypothesized that the abundances of benthic and pelagic FAD fishes are correlated and that there is a direct or indirect energetic link between shallow water pelagic and benthic fish assemblages near FADs.     

Biological interactions maintain the boundaries between kelp forests and urchin barrens in the Aleutian Archipelago

This study used benthic surveys and manipulative experiments to examine (1) if boundaries between kelp forests and urchin barrens exist at multiple locations spanning the Aleutian Archipelago, (2) if these boundaries are spatially stable, and (3) how changes in algal density within the kelp forests influence the ability of urchins to invade them. Our results demonstrate that sharply punctuated kelp forest-urchin barren boundaries occur throughout the Archipelago, and they are spatially stable for at least 2 years. Further, when all macroalgae were experimentally removed from the kelp forest side of the boundaries, urchins rapidly moved into these clearings and excluded macroalgae for up to 2 years. However, these movements were not observed where 75% or less of the macroalgae was removed (leaving 25% or more in place), suggesting that even low macroalgal abundances can prevent urchins from invading the kelp forests. Further, urchin densities were negatively related to kelp density, again indicating that kelp can reduce urchin densities. While the ability of urchins to overgraze kelp forests is widely known, our results indicate that kelp can inhibit urchins, that these inhibitory influences are a widely recurrent phenomenon, and that this interaction is important to maintaining kelp forests across the Aleutians.     

The survival of <Emphasis Type="Italic">Sicyopterus stimpsoni</Emphasis>, an endemic amphidromous Hawaiian gobiid fish,relies on the hydrological cycles of streams: evidence from changes in algal composition of diet through growth stages fish

Gut contents of larval, juvenile, and adult specimens of the Hawaiian gobiid fish Sicyopterus stimpsoni were examined to catalog the algal flora ingested by this species. The developmental stages of S. stimpsoni examined represented hallmark points in the fish’s life cycle corresponding with major migratory and metamorphic transitions. The algal flora was dominated by diatom species and shifted from taxa representative of a marine, planktonic community in larval fish to a freshwater, benthic community in juvenile and adult fish. This change in diet corresponds with the migration of larval fish to freshwater streams just prior to juvenile development in which rapid modification in mouth anatomy makes ingestion of planktonic algal species difficult. Benthic diatoms from juvenile and adult fish assemblages represented multiple genera that live in a narrow set of environmental conditions. These algae grow during a specific period in the development of the benthic algal community in Hawaiian streams. This suggests a highly specialized dietary behavior that depends heavily on continually restarting the benthic algal successional pattern, which appears to be regulated by the hydrological cycles of streams on the island.     

Seasonal rather than spatial variability drives planktonic and benthic bacterial diversity in a microtidal lagoon and the adjacent open sea

Coastal lagoons are highly productive ecosystems, which are experiencing a variety of human disturbances at increasing frequency. Bacteria are key ecological players within lagoons, yet little is known about the magnitude, patterns and drivers of diversity in these transitional environments. We carried out a seasonal study in the Venice Lagoon (Italy) and the adjacent sea, to simultaneously explore diversity patterns in different domains (pelagic, benthic) and their spatio‐temporal variability, and test the role of environmental gradients in structuring assemblages. Community composition differed between lagoon and open sea, and between domains. The dominant phyla varied temporally, with varying trends for the two domains, suggesting different environmental constraints on the assemblages. The percentage of freshwater taxa within the lagoon increased during higher river run‐off, pointing at the lagoon as a dynamic mosaic of microbial taxa that generate the metacommunity across the whole hydrological continuum. Seasonality was more important than spatial variability in shaping assemblages. Network analyses indicated more interactions between several genera and environmental variables in the open sea than the lagoon. Our study provides evidences for a temporally dynamic nature of bacterial assemblages in lagoons and suggests that an interplay of seasonally influenced environmental drivers shape assemblages in these vulnerable ecosystems.     

Can multitrophic interactions and ocean warming influence large‐scale kelp recovery?

Ongoing changes along the northeastern Atlantic coastline provide an opportunity to explore the influence of climate change and multitrophic interactions on the recovery of kelp. Here, vast areas of sea urchin‐dominated barren grounds have shifted back to kelp forests, in parallel with changes in sea temperature and predator abundances. We have compiled data from studies covering more than 1,500‐km coastline in northern Norway. The dataset has been used to identify regional patterns in kelp recovery and sea urchin recruitment, and to relate these to abiotic and biotic factors, including structurally complex substrates functioning as refuge for sea urchins. The study area covers a latitudinal gradient of temperature and different levels of predator pressure from the edible crab (Cancer pagurus) and the red king crab (Paralithodes camtschaticus). The population development of these two sea urchin predators and a possible predator on crabs, the coastal cod (Gadus morhua), were analyzed. In the southernmost and warmest region, kelp forests recovery and sea urchin recruitment are mainly low, although sea urchins might also be locally abundant. Further north, sea urchin barrens still dominate, and juvenile sea urchin densities are high. In the northernmost and cold region, kelp forests are recovering, despite high recruitment and densities of sea urchins. Here, sea urchins were found only in refuge habitats, whereas kelp recovery occurred mainly on open bedrock. The ocean warming, the increase in the abundance of edible crab in the south, and the increase in invasive red king crab in the north may explain the observed changes in kelp recovery and sea urchin distribution. The expansion of both crab species coincided with a population decline in the top‐predator coastal cod. The role of key species (sea urchins, kelp, cod, and crabs) and processes involved in structuring the community are hypothesized in a conceptual model, and the knowledge behind the suggested links and interactions is explored.     

Rocky intertidal fish communities of California: temporal and spatial variation

Synopsis We examined data from our own and published collections of intertidal and shallow littoral fishes of the North American Pacific Coast with respect to temporal and spatial trends in species composition and dominance. We compared (1) recent and past intertidal collections made five and seven years apart, respectively, for two California localities, (2) intertidal collections from twelve localities in California, Oregon, and British Columbia, and (3) intertidal versus subtidal collections at one California locality. Temporal comparisons indicated substantially lower abundance of the cottid Oligocottus snyderi at two California localities during 1984, at one locality due to depressed abundance of young. Interannual differences in abundances suggested that other tidepool fish assemblages undergo significant changes as well. Geographical comparisons indicated general similarity in species composition, with cottids predominating in tidepools although several other families also were well represented (e.g., Stichaeidae, Scorpaenidae). Eel-shaped stichaeids and pholids occurred at high densities in exposed boulder fields. Both the tidepool and boulder field assemblages showed north-south changes in species abundances. Comparison of collections from the intertidal and subtidal zones at one California locality demonstrated that fishes of these habitats form two essentially distinct assemblages, with most species restricted to or concentrated in one or the other habitat.     

Demography and feeding behavior of the kelp crab Taliepus marginatus in subtidal habitats dominated by the kelps Macrocystis pyrifera or Lessonia trabeculata

We studied the population and feeding ecology of the kelp crab Taliepus marginatus in subtidal kelp forests dominated by either of two morphologically different kelp species (Macrocystis pyrifera or Lessonia trabeculata) in northern Chile. The sizes and abundances of T. marginatus differed between the two kelp habitats. Kelp crabs were more abundant in the M. pyrifera forest than in the L. trabeculata forest. Size‐frequency distributions showed that juvenile and immature crabs were more common in the M. pyrifera forest than in the L. trabeculata forest, where reproductive adults predominated. The smaller crabs in the M. pyrifera habitat also consumed a higher proportion of kelp tissues than the larger crabs in the L. trabeculata habitat, which had a higher proportion of animal food in their diet. In both kelp forests, individuals of T. marginatus showed a similar pattern of nocturnal feeding over a 24‐h period, consuming more food at night than during the day. The more complex and dense forests of M. pyrifera appear to present better nursery habitats for juvenile kelp crabs than the more open and less dense forests dominated by L. trabeculata. These results suggest that the role of the two kelp habitats for T. marginatus varies during the life cycle of the kelp crabs, with M. pyrifera tending to have nursery function and L. trabeculata being more suitable as a reproductive habitat.     

<Emphasis Type="Italic">Lacuna vincta</Emphasis> (Mollusca,Neotaenioglossa) herbivory on juvenile and adult <Emphasis Type="Italic">Nereocystis luetkeana</Emphasis> (Heterokontophyta,Laminariales)

Herbivory can be an important factor structuring coastal algal communities. Herbivores may preferentially graze particular algal species or tissue types. Mesograzers, despite their small size, can critically weaken kelp thalli and impact entire kelp beds. We propose that when kelp beds are composed of several kelp cohorts, mesograzers will selectively choose to inhabit younger plants and grazing activities will have a greater impact on younger plants. This study investigated the effects of grazing by the littorinid gastropod, Lacuna vincta, on different age classes of the bull kelp, Nereocystis luetkeana by (1) testing food preference of L. vincta on juvenile, first-year adult, and second-year adult Nereocystis blades in the laboratory, (2) determining substrate (blades of different ages) preference of L. vincta in the laboratory, and by (3) estimating in-situ herbivore abundances and densities on juvenile and adult Nereocystis. Results demonstrated that grazing by L. vincta produced greater damage on juvenile than older Nereocystis tissues. Although L. vincta did not select juvenile versus older kelps as substrate in the laboratory, in situ surveys showed that differences existed between age classes with higher L. vincta densities on juvenile than adult kelp. We conclude that at a local scale, L. vincta can be an important structuring factor in Nereocystis populations due to its high density and grazing ability. Handling editor: K. Martens     

Spatial and annual variation in the diets of juvenile smallmouth bass, Micropterus dolomieu

Synopsis We measured macroinvertebrate densities and abundance, size, and diet of juvenile smallmouth bass, Micropterus dolomieu, at five sites located at varying distances from a metalimnetic release dam. We used these data to determine the influence of high prey abundances on stomach fullness and age-0 year-class strength. Summer diets of juvenile smallmouth bass (27.7–107.7 mm total length) were dominated by Ephemeroptera (primarily Baetidae) but diet composition was highly variable among years and sites. A linear index of prey selection showed that Ephemeroptera were preferred and Trichoptera were avoided at all sites in all years; but, selection indices were not consistent for Chironomidae or Amphipoda and Isopoda. In two of three years, stomach fullness (gut content mass relative to predicted maximum) of juvenile smallmouth bass decreased with distance downstream of the dam, which reflected patterns observed in benthic macroinvertebrate densities. However, in 1989 when flooding and increased turbidity reduced abundances of juvenile smallmouth bass, no differences in stomach fullness were found among sites. High stomach fullness of juvenile smallmouth bass was attributed to high prey abundances near the dam in years of low or normal streamflow. However, patterns in juvenile smallmouth bass abundances in mid-summer could not be attributed to longitudinal variation in prey abundance.     

Environmental variability, early life-history traits, and survival of new coral reef fish recruits

For benthic marine organisms with complex life cycles, conditionsexperienced by pelagic larvae can influence juvenile survival.Trait-specific selective mortality has been documented in thelaboratory and field, yet our knowledge of the factors contributingto the existence, strength, and consistency of natural selectivemortality is limited. We compiled previously published and unpublisheddata on the common Caribbean coral reef fish, Thalassoma bifasciatum,recruiting to Barbados, West Indies, and the upper Florida Keysto examine how environmental variability during pelagic larvallife influences the distribution of early life-history traitsexhibited by new recruits. We explored how the scope of variabilityin otolith-derived traits such as larval growth, pelagic larvalduration (PLD), size and condition at settlement, and earlyjuvenile growth influences the degree to which mortality ofjuveniles is selective. At both locations, contrasting oceanographicconditions (periodic passage of large low-salinity North BrazilCurrent [NBC] rings near Barbados and seasonal variation inwater temperature at Florida) led to significant differencesin the early life-history traits of recruits. Mortality wasmost frequently selective for the two most variable traits,condition at settlement and early juvenile growth. Environmentalvariability (including variation in predation pressure and stress-inducingconditions) also likely influences juvenile mortality and consequentlythe degree to which selective loss of particular traits occurs.As we begin to better understand the spatial, temporal, andspecies-specific circumstances in which events occurring duringlarval life influence juvenile performance, studies must alsobe extended to examine how these processes are translated intoadult fitness.     

Relative abundances of living and dead molluscs in two Californian lagoons

Assemblages of living benthic invertebrates (predominantly bivalve molluscs) from the sand-channel habitat of two Southern California (U.S.A.) lagoons were sampled on ten occasions over a 37-month period. A one-time sampling of the corresponding assemblages of accumulating dead remains made possible a contrast of living and dead assemblages designed to assess the biasing effects of post-mortem transportation, shell dissolution, and time-averaging. Species-by-species comparisons of the living and dead molluscs found together in the same samples strongly suggested that post-mortem transportation is insignificant within this high-energy habitat. A similar conclusion arose from contrasting the pattern of spatial heterogeneity of the living community with that of the dead assemblage. Species presence-and-absence comparisons were generally more reliable than comparisons of relative abundances. Adjustments for experimentally determined rates of post-mortem shell dissolution proved significant and further decreased the correspondence in relative abundances between living and dead assemblages. Greater temporal variability of living populations at Mugu Lagoon, probably caused by a more harsh physical environment, increased the differences in composition between living and dead assemblages, which suggests that correspondence in relative abundances between living and dead assemblages generally should be expected to decrease as the life environment becomes more harsh.     

Zooplankton community structure in the kelp beds of the sub-Antarctic Prince Edward Archipelago: are they a refuge for larval stages?

Kelp beds are thought to provide a refuge for a variety of marine organisms by damping waves, changing hydrodynamic flow, offering substrata for epiphytic species, and altering the abundances of predators and prey. At the sub-Antarctic Prince Edward Islands, a typical flow-through system, kelp beds have the potential of acting as a prime habitat for a variety of pelagic species that would otherwise be swept away and lost from the island ecosystem. The current study investigates the effects of kelp beds on the abundance and composition of zooplankton and microphytoplankton, with the main aim of determining whether kelp beds act as a repository for larval stages in general, and for the swimming prawn, Nauticaris marionis, in particular. Salinity gradients created by freshwater run-off indicated that kelp beds at Marion Island retain surface water and restrict water exchange with the open ocean. Both the abundance and diversity of zooplankton were greatest within the kelp beds. This was partially due to the high abundance of kelp-associated species, but also to the apparent retention of naupliar larvae within the kelp canopy. Unlike the larvae of ostracods and copepods, caridean zoeae were rare, indicating that kelp beds are not a prime habitat for larvae of N. marionis. The larval retention mechanism for this species, therefore, remains unknown. Apart from retaining water and certain species of zooplankton, chlorophyll a/phaeopigment ratios confirmed the existence of a substantial detrital pool within the kelp beds. This retention of detritus may explain the observed importance of kelp-derived matter in the diet of many nearshore animals. In contrast to the zooplankton, kelp beds seemed to have little effect on the abundance and composition of microphytoplankton, and chlorophyll a values were low at all stations.     

The Great Melting Pot. Common Sole Population Connectivity Assessed by Otolith and Water Fingerprints

Quantifying the scale and importance of individual dispersion between populations and life stages is a key challenge in marine ecology. The common sole (Solea solea), an important commercial flatfish in the North Sea, Atlantic Ocean and the Mediterranean Sea, has a marine pelagic larval stage, a benthic juvenile stage in coastal nurseries (lagoons, estuaries or shallow marine areas) and a benthic adult stage in deeper marine waters on the continental shelf. To date, the ecological connectivity among these life stages has been little assessed in the Mediterranean. Here, such an assessment is provided for the first time for the Gulf of Lions, NW Mediterranean, based on a dataset on otolith microchemistry and stable isotopic composition as indicators of the water masses inhabited by individual fish. Specifically, otolith Ba/Ca and Sr/Ca profiles, and δ¹³C and δ¹⁸O values of adults collected in four areas of the Gulf of Lions were compared with those of young-of-the-year collected in different coastal nurseries. Results showed that a high proportion of adults (>46%) were influenced by river inputs during their larval stage. Furthermore Sr/Ca ratios and the otolith length at one year of age revealed that most adults (∼70%) spent their juvenile stage in nurseries with high salinity, whereas the remainder used brackish environments. In total, data were consistent with the use of six nursery types, three with high salinity (marine areas and two types of highly saline lagoons) and three brackish (coastal areas near river mouths, and two types of brackish environments), all of which contributed to the replenishment of adult populations. These finding implicated panmixia in sole population in the Gulf of Lions and claimed for a habitat integrated management of fisheries.     

Depth distribution of nearshore temperate fish larval assemblages near rocky substrates

In this study, we compare the composition, abundance and structureof a temperate fish larval assemblage at different depth intervals(0–4, 4–8 and 8–12 m) in the extreme nearshoreenvironment. We used a plankton net attached to an underwaterscooter to sample in close proximity to the rocky substrate(<50 cm). A total of 868 larvae from 27 taxa in 13 familieswere caught. The majority of larvae belonged to benthic reef-associatedspecies (Blenniidae, Gobiidae, Gobiesocidae and Tripterygiidae),the four most abundant comprising 76% of the total larvae caught.A non-metric multidimensional scaling analysis (MDS) showedthat there was a single multispecific larval patch near thesubstrate in the extreme nearshore up to 12 m depth. Nonetheless,distinct larval abundances were found in this relatively smalldepth range, with the majority of species being more abundantat the deepest interval, particularly Pomatoschistus pictusand Gobius xanthocephalus. Tripterygion delaisi was an exceptionbeing more abundant at the shallowest depth as young larvae.The density of pre-flexion larvae was not significantly differentacross depth intervals, but post-flexion larval density increasedwith depth. The full size range (from hatching to settlement)of P. pictus was present at the extreme nearshore. The innovativesampling technique used here revealed high densities of larvaeclose to the bottom, and depth was found to be an importantfactor influencing the distribution of several taxa and ontogeneticstages. The nearshore component of coastal fish larval assemblagesnear rocky substrates has been poorly studied, and our resultssuggest that the high densities of larvae found to aggregatein these environments must be taken into account when studyingdistribution and functional aspects of these assemblages.     

Seasonal variation in epifaunal communities associated with giant kelp (Macrocystis pyrifera) at an upwelling‐dominated site

Kelp forests are highly productive and species‐rich benthic ecosystems in temperate regions that provide biogenic habitat for numerous associated species. Diverse epifaunal communities inhabit kelp sporophytes and are subject to variations in the physical environment and to changes experienced by the kelp habitat itself. We assessed seasonal variations in epifaunal invertebrate communities inhabiting giant kelps, Macrocystis pyrifera, and their effects on this seaweed. Six seasonal samplings were conducted over a year at an upwelling‐dominated site in northern‐central Chile where physical conditions are known to fluctuate temporally. More than 30 taxa were identified, among which peracarid crustaceans stood out in both diversity and abundance. Species richness and abundance differed among sporophyte sections (holdfast and fronds) and throughout the year. The frond community was dominated by two grazers (the amphipod Peramphithoe femorata and the isopod Amphoroidea typa), while suspension feeders, grazers, and omnivores (the amphipod Aora typica, the isopod Limnoria quadripunctata, and polychaetes) dominated the holdfasts. Abundances of the dominant species fluctuated throughout the year but patterns of variation differed among species. The most abundant grazer (P. femorata) had highest densities in summer, while the less abundant grazer (A. typa) reached its peak densities in winter. Interestingly, the area of kelp damaged by grazers was highest in autumn and early winter, suggesting that grazing impacts accumulate during periods of low kelp growth, which can thus be considered as ‘vestiges of herbivory past.’ Among the factors determining the observed seasonal patterns, strong variability of environmental conditions, reproductive cycles of associated fauna, and predation by fishes vary in importance. Our results suggest that during spring and early summer, bottom‐up processes shape the community structure of organisms inhabiting large perennial seaweeds, whereas during late summer and autumn, top‐down processes are more important.     

Long Term Variability in the Structure of Kelp Communities in Northern Chile and the 1997–98 ENSO

This is the first study on the south eastern Pacific coast of South America which details long term, interannual variability in the structure of subtidal rocky-bottom kelp-dominated communities before, during, and after the El Niño Southern Oscillation (ENSO) event of 1997–1998 in northern Chile (23^°S). The temporal patterns of the main components of these ecosystems, which included Macrocystis integrifolia, Lessonia trabeculata, echinoids and asteroids, were evaluated seasonally between 1996 and 2004. M. integrifolia demonstrated high interannual variability in temporal patterns of abundance. The 1997–1998 ENSO did not significantly modify the temporal patterns of Macrocystis, although local extinction of M. integrifolia beds occurred during negative thermal anomalies in 1999–2000 (La Niña event), facilitating the establishment of urchin dominated “barren grounds”. The abundance of Lessonia trabeculata showed little temporal variability, and this species dominated the deeper regions of the kelp assemblage (8–13 m depth). The structure of the kelp communities in the study area is regulated by a trophic cascade which modulates alternation between kelp dominated areas and sea urchin barrens. In this context, frequent and intense upwelling of cold water high in nutrients favors the establishment and persistence of kelp assemblages. During ENSO, coastal upwellings can mitigate superficial warming of coastal water and increase the nutrient concentration in the water column. Superficial warming during the 1997–1998 ENSO induced spawning by different species of echinoderms, which resulted in major recruitment of these species during 1999. Top-down events, such as the decrease in densities of the asteroids after the 1997–1998 ENSO event, favored increases in densities of benthic grazers, which caused significant decreases in abundance of M. integrifolia. The re-establishment of the adult fraction of the carnivore (starfish) guild coincided with a decrease in the density of sea urchins and thus re-establishment of the kelp. In the temperate south eastern Pacific, oceanographic events, which act on different spatial-temporal scales, trigger trophic cascades that act at local levels, producing interannual variability in the structure of kelp communities. On the other hand, considering the high macroinvertebrate diversity associated with kelp assemblages, the transitions between kelp-dominated areas and sea urchin barrens do not appear to significantly affect the biodiversity of these assemblages of benthic invertebrates.     

Oceanographic and lunar forcing affects nearshore larval fish assemblages from temperate rocky reefs

The influence of oceanographic features and moon phases on ichthyoplankton assemblages in a temperate nearshore rocky reef off El Quisco Bay, central Chile, was assessed during austral spring–summer 2015–2016 using Bongo nets. Wind direction was predominantly south-west, and ocean temperature increased gradually during the study period, fluctuating between 11.6°C and 17.7°C. A relatively cold period (from late September to early December, 12.42?±?0.64°C) was distinguished from a relatively warmer phase (from mid-December to February, 13.56?±?1.08°C). Nearshore ichthyoplankton was composed of 13,700 individuals, belonging to 43 taxa. Larval Strangomera bentincki (Clupeidae) were collected in high numbers between late September and late October with peaks during full moon and first quarter (maximum?=?734 ind. 100?m^?3); larval Engraulis ringens (Engraulidae) was most abundant between late October and late December 2015, with peaks during the third quarter and full moon. Principal Component Analysis of ichthyoplankton data explained more than 44% of total variance and showed the influence of cold/warm periods in the structuring of larval fish assemblages. Water temperature had more influence than lunar phase in the structure and composition of nearshore fish larvae off central Chile. We conclude that larval fish assemblages found in nearshore waters change on a seasonal scale by differences in the reproductive activity among species, and that lunar phase exerts a low, but significant effect on the abundance of fish larvae, but this variability is species-specific.