<Emphasis Type="Italic">Macrocystis integrifolia</Emphasis> and <Emphasis Type="Italic">Lessonia trabeculata</Emphasis> (Laminariales; Phaeophyceae) kelp habitat structures and associated macrobenthic community off northern Chile

Macrocystis integrifolia and Lessonia trabeculata form vast kelp beds providing a three-dimensional habitat for a diverse invertebrate and fish fauna off northern Chile. Habitat modifications caused by the El Niño Southern Oscillation (ENSO) are likely to alter the inhabiting communities. The aim of this study was to reveal relationships between distinct habitat structures of a M. integrifolia kelp bed, a dense L. trabeculata kelp bed and L. trabeculata patches colonizing a barren ground, and the associated dominant macrobenthic key species. Seasonally 15 sampling units (10 m² each) of any of the three habitats were monitored by SCUBA divers, which counted sporophytes and macroinvertebrates living between the latter. Furthermore, samples of plants were analysed in the laboratory to measure the morphological variables: total plant length, maximal holdfast diameter, stipe number, number of dichotomies per stipe, frond width and total drained wet mass. Multivariate analysis showed that the L. trabeculata kelp bed is denser, with a higher number of dichotomies per stipe, whereas sporophytes of M. integrifolia are longer with more stipes and wider fronds. Sporophytes of L. trabeculata patchily present on barren ground are shorter and have more stipes compared with those in the dense L. trabeculata kelp bed. Thus, the habitats provide different three-dimensional structures. The associated macrobenthic communities show a variable degree of overlapping; however, key faunal assemblages were distinguished for each habitat. Our study provides evidence that habitat diversity drives species diversity, the more homogeneous, monospecifically composed kelp bed habitats show comparatively low diversity, mainly caused by the dominance of the ascidian P. chilensis and T. tridentata in the M. integrifolia bed, and the mussel A. ater only present in the L. trabeculata bed. Species richness and diversity is highest in the heterogeneous habitat where L. trabeculata patches interrupt the barren ground. Our study revealed morphological differences between M. integrifolia and L. trabeculata kelp beds reflected in stipe number, plant length, dichotomies per stipe, and wet mass, which influence the composition of the associated characteristic fauna and its functional relations i.e. T. niger and T. tridentata.     

Arctic rhodolith beds and their environmental controls (Spitsbergen, Norway)

Coralline algae (Corallinales, Rhodophyta) that form rhodoliths are important ecosystem engineers and carbonate producers in many polar coastal habitats. This study deals with rhodolith communities from Floskjeret (78°18′N), Krossfjorden (79°08′N), and Mosselbukta (79°53′N), off Spitsbergen Island, Svalbard Archipelago, Norway. Strong seasonal variations in temperature, salinity, light regime, sea-ice coverage, and turbidity characterize these localities. The coralline algal flora consists of Lithothamnion glaciale and Phymatolithon tenue. Well-developed rhodoliths were recorded between 27 and 47 m water depth, while coralline algal encrustations on lithoclastic cobbles were detected down to 77 m water depth. At all sites, ambient waters were saturated with respect to both aragonite and calcite, and the rhodolith beds were located predominately at dysphotic water depths. The rhodolith-associated macrobenthic fauna included grazing organisms such as chitons and echinoids. With decreasing water depth, the rhodolith pavements were regularly overgrown by non-calcareous Polysiphonia-like red algae. The corallines are thriving and are highly specialized in their adaptations to the physical environment as well as in their interaction with the associated benthic fauna, which is similar to other polar rhodolith communities. The marine environment of Spitsbergen is already affected by a climate-driven ecological regime shift and will lead to an increased borealization in the near future, with presently unpredictable consequences for coralline red algal communities.     

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.     

Epifaunal and algal assemblages associated with the native Chondrus crispus (Stackhouse) and the non-native Grateloupia turuturu (Yamada) in eastern Long Island Sound

Although the spread of non-native algae is rapidly escalating, relatively few ecological studies have been done to gauge the impacts incurred to native flora and fauna. A reduction in the dominance of a native habitat-forming macroalga due to the replacement by an introduced species can have adverse effects on the community. The non-native red alga Grateloupia turuturu, first reported in Rhode Island, USA in 1994, has since extended its southern range into eastern Long Island Sound. This large alga has the potential to impact coastal communities by altering the floristic composition important to associated flora and fauna. A comparison of algal and epifaunal assemblages was made during 2006 and 2007 between native and non-native algal communities dominated by either G. turuturu or the native, Chondrus crispus at two sites in Long Island Sound. We found that within Grateloupia-dominated habitat, there was a large decrease in overall macrophyte biomass as compared to native habitat. We also found that habitat dominated by the non-native alga reduced species richness and total abundance of invertebrates relative to nearby habitats dominated by C. crispus. In addition, we found that the dominant mesofaunal species, important to higher trophic level consumers, had greatly reduced densities in communities dominated by the non-native alga.     

The inshore marine ecosystem off the Vestfold Hills,Antarctica

The planktonic, ice/water interface, and benthic communities at three sites off the coast of the Vestfold Hills, Antarctica, were examined over a complete year.The planktonic flora and fauna were composed predominantly of oceanic species with diatoms and copepods the numerically dominant groups. Primary production was largely restricted to the summer months except for epontic algae which developed in spring. The zooplankton exhibited a similar seasonal cycle but lagged some months behind that of the phytoplankton.The ice/water interface (epontic) fauna consisted of species from the plankton and benthos. Copepods were major contributors; however, two amphipod species dominated. Seasonality of the fauna in this habitat was determined by ice formation and breakout, and development of ice algae.Each of the benthic substrates supported a characteristic macrofaunal assemblage, although infaunal amphipods and tanaids were similar at each site. Infauna exhibited a distinct seasonal cycle related to that of the primary producers whereas macrofauna showed no seasonal changes in abundance.Species composition of each community in this coastal antarctic region was comparable with that of similar habitats in other antarctic coastal areas, supporting the circumpolarity of antarctic marine communities.     

Alteration of Sexual Reproduction and Genetic Diversity in the Kelp Species Laminaria digitata at the Southern Limit of Its Range

Adaptation to marginal habitats at species range-limits has often been associated with parthenogenetic reproduction in terrestrial animals and plants. Laboratory observations have shown that brown algae exhibit a high propensity for parthenogenesis by various mechanisms. The kelp Laminaria digitata is an important component of the ecosystem in Northern European rocky intertidal habitats. We studied four L. digitata populations for the effects of marginality on genetic diversity and sexual reproduction. Two populations were marginal: One (Locquirec, in Northern Brittany) was well within the geographic range, but was genetically isolated from other populations by large stretches of sandy beaches. Another population was at the range limits of the species (Quiberon, in Southern Brittany) and was exposed to much higher seasonal temperature changes. Microsatellite analyses confirmed that these populations showed decreased genetic and allelic diversity, consistent with marginality and genetic isolation. Sporophytes from both marginal populations showed greatly diminished spore-production compared to central populations, but only the southern-limit population (Quiberon) showed a high propensity for producing unreduced (2N) spores. Unreduced 2N spores formed phenotypically normal gametophytes with nuclear area consistent with ≥2N DNA contents, and microsatellite studies suggested these were produced at least in part by automixis. However, despite this being the dominant path of spore production in Quiberon sporophyte individuals, the genetic evidence indicated the population was maintained mostly by sexual reproduction. Thus, although spore production and development showed the expected tendency of geographical parthenogenesis in marginal populations, this appeared to be a consequence of maladaptation, rather than an adaptation to, life in a marginal habitat.     

Patterns of abundance and assemblage structure of epifauna inhabiting two morphologically different kelp holdfasts

The mobile fauna associated with two sympatric kelp species with different holdfast morphology (Saccorhiza polyschides and Laminaria hyperborea) was compared to test for differences in the assemblage structure of holdfast-associated mobile epifauna. A total of 24,140 epifaunal individuals were counted from 30 holdfasts of each kelp species. Overall epifaunal abundances exceeded faunal abundances previously reported from holdfasts of other kelps. Three taxonomic groups, Amphipoda, Mollusca, and Polychaeta, accounted for ca. 85% of all individuals. Total abundances increased with the amount of habitat available, quantified either as the volume or the area provided by the holdfasts. The multivariate structure of the epifaunal assemblage did not differ between holdfasts of the two kelp species. However, epifaunal assemblages responded differentially to the habitat attributes provided by each type of kelp holdfast: multivariate variation in the assemblage structure of epifauna was mostly explained by holdfast area and volume for L. hyperborea, and by the surface-to-volume ratio for S. polyschides holdfasts. Therefore, the physical attributes of biogenic habitats, here kelp holdfasts that better predict patterns in the assemblage structure of associated fauna can differ according to their different physical morphology, even though the overall assemblage structure of associated fauna was similar.     

Seasonal sea ice cover as principal driver of spatial and temporal variation in depth extension and annual production of kelp in Greenland

We studied the depth distribution and production of kelp along the Greenland coast spanning Arctic to sub‐Arctic conditions from 78 ºN to 64 ºN. This covers a wide range of sea ice conditions and water temperatures, with those presently realized in the south likely to move northwards in a warmer future. Kelp forests occurred along the entire latitudinal range, and their depth extension and production increased southwards presumably in response to longer annual ice‐free periods and higher water temperature. The depth limit of 10% kelp cover was 9–14 m at the northernmost sites (77–78 ºN) with only 94–133 ice‐free days per year, but extended to depths of 21–33 m further south (73 ºN–64 ºN) where >160 days per year were ice‐free, and annual production of Saccharina longicruris and S. latissima, measured as the size of the annual blade, ranged up to sevenfold among sites. The duration of the open‐water period, which integrates light and temperature conditions on an annual basis, was the best predictor (relative to summer water temperature) of kelp production along the latitude gradient, explaining up to 92% of the variation in depth extension and 80% of the variation in kelp production. In a decadal time series from a high Arctic site (74 ºN), inter‐annual variation in sea ice cover also explained a major part (up to 47%) of the variation in kelp production. Both spatial and temporal data sets thereby support the prediction that northern kelps will play a larger role in the coastal marine ecosystem in a warmer future as the length of the open‐water period increases. As kelps increase carbon‐flow and habitat diversity, an expansion of kelp forests may exert cascading effects on the coastal Arctic ecosystem.     

Contrasting genetic diversity patterns in two sister kelp species co‐distributed along the coast of Brittany,France

We investigated patterns of genetic structure in two sister kelp species to explore how distribution width along the shore, zonation, latitudinal distribution and historical factors contribute to contrasting patterns of genetic diversity. We implemented a hierarchical sampling scheme to compare patterns of genetic diversity and structure in these two kelp species co‐distributed along the coasts of Brittany (France) using a total of 12 microsatellites, nine for Laminaria hyperborea and 11 for Laminaria digitata, of which eight amplified in both species. The genetic diversity and connectivity of L. hyperborea populations were greater than those of L. digitata populations in accordance with the larger cross‐shore distribution width along the coast and the greater depth occupied by L. hyperborea populations in contrast to L. digitata populations. In addition, marginal populations showed reduced genetic diversity and connectivity, which erased isolation‐by‐distance patterns in both species. As L. digitata encounters its southern range limit in southern Brittany (SBr) while L. hyperborea extends down to mid‐Portugal, it was possible to distinguish the effect of habitat continuity from range edge effects. We found that L. digitata did not harbour high regional diversity at its southern edge, as expected in a typical rear edge, suggesting that refuges from the last glacial maximum for L. digitata were probably not located in SBr, but most likely further north. For both species, the highest levels of genetic diversity were found in the Iroise Sea and Morlaix Bay, the two regions in which they are being currently harvested. Preserving genetic diversity of these two foundation species in these areas should, thus, be a priority for the management of this resource in Brittany.     

Regime shifts in vegetation composition of Baltic Sea coastal lagoons

Vegetation communities, morphometric and water quality variables were sampled in 62 undisturbed coastal lagoons along a natural land-uplift gradient in the northern Baltic Sea. The lagoons had a morphological inlet threshold reflecting habitat isolation (i.e. the diminished connectedness of the lagoon to the sea) and located in different parts of the archipelago (corresponding to altering wave exposure). We used indirect multivariate methods to find changes in vegetation composition, and axes derived from the analyses were used in correlation and stepwise multiple regression analyses together with environmental variables. Habitat isolation proved to be the strongest predictor for vegetation composition. To identify significant change-points we used a method, which detects regime shifts by accounting for differences in chronological series and gives a regime shift index. Significant shifts in habitat isolation, average depth and total nitrogen were followed by shifts in species variables (i.e. dominant species, cover and species richness) and salinity, total phosphorus and turbidity. Of the species, especially Chara tomentosa showed a shift of high magnitude. Also a shift in wave exposure mirroring position of lagoons in the archipelago structured the species, but this division was seen only for less isolated lagoons. Our results suggest that lagoons are primarily structured by habitat isolation forming two structurally different regimes: one of less isolated lagoons dominated by a diverse array of vascular plants and marine algae of both outer and inner archipelago characters, and one with isolated lagoons dominated by high vegetation cover and dominance of Chara. In addition, vegetation seemed to stabilize water quality in the isolated regime by reducing turbidity and phosphorus, indicating a potential feed-back mechanism and a shift in structuring disturbances from abiotic to biotic factors with habitat isolation.     

Diurnal, horizontal and vertical dispersal of kelp-associated fauna

The kelp Laminaria hyperborea is host for a rich fauna of mobile invertebrates. Dispersal patterns of these animals may be crucial for their availability to visual predators like fish, which are known to search for food in these productive habitats. Diurnal, horizontal and vertical dispersal within and out of the kelp forest were studied by analysing colonization of artificial substrata placed among kelps. The species composition of the fauna was different on three parts of the kelp: lamina, stipes (with epiphytes) and holdfast. The artificial substrata were colonized mainly by species associated with kelp. More species and individuals colonized the artificial substrata at night than during the day. The most abundant faunal groups on the kelps and the artificial substrata were amphipods and gastropods. Both groups dispersed at a significantly higher rate at night than during the day. Rapid horizontal dispersal out of the kelp forest was found. The artificial substrata were also colonized quickly by kelp fauna at all vertical levels inside and above the kelp forest. However, species associated with the kelp holdfast tended to disperse close to the bottom, while stipe-associated fauna moved through all parts of the kelp forest and even above the canopy layer. A high dispersal rate appears common amongst the mobile species living on kelp and seems to be advantageous, despite the risks involved in emigrating from the habitat and being exposed to predators. Higher activity at night may reduce availability to predators.     

An overview of the Tasmanian geometrid moth fauna (Lepidoptera: Geometridae) and its conservation status

A brief review of the geometrid fauna of the large island of Tasmania and a simple analysis of its conservation status and threats are presented. The fauna comprises 310 species of which Ennominae contribute slightly less than half the total and Larentiinae one third; 23% of the geometrid fauna is endemic at species level. Mixed eucalypt-rainforest is identified as the richest wet forest habitat in geometrid species. Using distribution data at 10  km resolution, the most widespread and most restricted taxa are identified. The conservation status of Lepidoptera living above 800 m is relatively good. However, coastal species and those associated with herb-rich native grasslands are under some pressure from habitat change. Three species of geometrid moths are listed as threatened in Tasmania’s Threatened Species Protection Act 1995 but several others may qualify for listing.     

Ecological Drivers of Shark Distributions along a Tropical Coastline

As coastal species experience increasing anthropogenic pressures there is a growing need to characterise the ecological drivers of their abundance and habitat use, and understand how they may respond to changes in their environment. Accordingly, fishery-independent surveys were undertaken to investigate shark abundance along approximately 400 km of the tropical east coast of Australia. Generalised linear models were used to identify ecological drivers of the abundance of immature blacktip Carcharhinus tilstoni/Carcharhinus limbatus, pigeye Carcharhinus amboinensis, and scalloped hammerhead Sphyrna lewini sharks. Results indicated general and species-specific patterns in abundance that were characterised by a range of abiotic and biotic variables. Relationships with turbidity and salinity were similar across multiple species, highlighting the importance of these variables in the functioning of communal shark nurseries. In particular, turbid environments were especially important for all species at typical oceanic salinities. Mangrove proximity, depth, and water temperature were also important; however, their influence varied between species. Ecological drivers may promote spatial diversity in habitat use along environmentally heterogeneous coastlines and may therefore have important implications for population resilience.     

Species richness in macroalgae and macrofauna assemblages on Fucus serratus L. (Phaeophyceae) and Zostera marina L. (Angiospermae) in Skagerrak, Norway

The macrophytes Fucus serratus and Zostera marina form similar substrates for associated flora and fauna in shallow waters in Norway. While F. serratus forms a more or less continuous belt on rocky substrate along the coast, Z. marina forms disjunct populations on sandy or muddy bottoms. This study focused on the organisms associated with these two macrophytes in two localities in the Skagerrak region. In total, 130 taxa of epiphytic organisms were identified: 22 green algae, 41 red algae, 32 brown algae, eight diatoms and 27 sessile animals. One hundred and twenty-seven taxa of mobile macrofauna were registered. The dominant group was crustaceans, with amphipods as the order containing most species. Many species of both plants and animals preferred one or the other habitat. It is concluded that coastal macrophyte systems have high species diversity.     

Spatio-temporal distribution patterns and conservation of fish assemblages in a Chilean coastal river

River environments are characterized by extreme spatial and temporal variation in the physical environment. The relationship of fish assemblages to environmental variation is poorly understood in many systems. In Chile zonation patterns of fish assemblages have been documented in several Andean river drainages. Coastal river drainages are comparatively small, but inordinately important because of their highly endemic flora and fauna and their proximity to major human populations. For conservation purposes it is important to understand what environmental factors affect assemblage structure of fishes especially in the comparatively high diversity coastal drainages. We studied patterns of fish distribution and abundance in three rivers of the coastal, Andalien drainage near Concepción, Chile. We used multi-dimensional scaling analyses to compare patterns among zones (rithron, transition and potamon) and high and low flow seasons. Species assemblages differed by zone, but not with season. Assemblages consisted of nested subsets of species characterized by their range of distribution among zones. One species group was composed of widespread species that occurred in all three zones, another species group consisted of species found only in transitional and potamal zones, and a final group was comprised of species found only in the potamal zone. The potamal zone contained the most diverse and abundant fish assemblage. Fish assemblages were related to both water quality and habitat structure variables. This study suggests that the key to conserving the diversity of native fish communities in coastal Chilean rivers is in the conservation of potamal regions. Unfortunately, most protected areas in Chile are in the depauperate headwaters of drainages. Protection of only headwaters is clearly inadequate and will not contribute to the conservation of this unique freshwater fish fauna.     

Checklist of fauna found in zooplankton samples from the Barents Sea

We present a list of zooplankton taxa occurring in the Barents Sea based on our analysis of 360 samples from the upper 100 m of the water column as well as on reports from published sources. Moreover, we provide information on adult size, ecological and geographical distribution, habitat preference and frequency of occurrence of each taxon. The list encompasses a total of 374 species and higher taxa. Most are mesozooplankton, with Copepoda prevailing (153 species), and belong to the holoplankton. However, pseudoplankton, organisms only circumstantially occurring in the water column, also comprise a significant part of the fauna (86 taxa). The coastal zooplankton (264 neritic species) was richer than the fauna of the open sea. In our samples, the majority of the zooplankton taxa were rarely found (94 of 157 taxa, equivalent of 60%), 46 taxa (29%) were moderate and only 17 taxa (11%) were common (found in >80% of the samples). Among these, the copepods Calanus finmarchicus, C. glacialis, Oithona similis and Pseudocalanus minutus were most frequent.     

The invertebrate fauna of epiphyte mats in the canopy of northern rata (Myrtaceae: Metrosideros robusta A. Cunn.) on the West Coast of the South Island,New Zealand

Abstract

The range of microhabitats and microclimatic conditions provided by epiphytes has been linked to the high diversity of invertebrates in many forest canopies worldwide, but comparably little is known about the invertebrate fauna in this habitat in New Zealand. This study compiled an inventory of the invertebrate fauna of epiphyte mats in the canopy of northern rata (Myrtaceae: Metrosideros robusta A. Cunn.) at two study sites on the West Coast of the South Island. A total of 242 069 invertebrate specimens was collected over one year, representing 4 phyla, 9 classes and more than 160 families, 225 genera and 446 species. At least 10 new species and 3 new genera were identified, while 5 species were recorded outside their known geographical range. Epiphyte mats provided habitat for an invertebrate fauna, highly diverse and abundant both taxonomically and functionally, dominated in terms of abundance by Acari, Collembola and Hymenoptera (largely ants), and in terms of feeding guilds by epiphyte grazers and ants. As the first inventory of this taxonomic depth and breadth compiled for New Zealand forest epiphyte habitats, this study provides important baseline data for the conservation of biodiversity in New Zealand's indigenous forests.     

三沙湾浮游动物生态类群演替特征

根据2010年6月-2011年5月三沙湾海域5个航次海洋综合调查资料,对三沙湾浮游动物种群特征进行分析,并与我国不同纬度海湾生态类群结构进行比较.探讨三沙湾海域浮游动物生态类群季节变化特征及其受水团季节变化的影响.研究结果表明:4月和5月三沙湾海域主要受到浙闽沿岸流影响,生物多样性H'指数分别为2.03和2.02;种类数分别仅为17种和19种,明显低于6月、8月和10月;浮游动物生态类群以暖温带近海种为主;优势种种类数少,单一优势种优势性明显,4月中华哲水蚤丰度占浮游动物总丰度的65.03％;群落结构特征与同期我国长江口浮游动物区系特征相似.6月三沙湾海域受到浙闽沿岸流和台湾暖流共同影响,同时因闽北雨季导致大量大陆径流汇入,使得该月浮游动物种群结构复杂,生物多样性指数和种类数全年最高,为3.12和45种,与5月相比,种类更替明显,物种更替率为69.39％;亚热带近海种丰度百分比最高(73.03％),亚热带外海种种类数百分比次之(48.89％),是海域浮游动物生态类群由以暖温带近海种为主向以亚热带外海种为主的过渡时期.8月和10月浙闽沿岸流消失,三沙湾海域受台湾暖流控制,海水温度和盐度升高,生物多样性指数和种类数均略低于6月;生态类群结构以亚热带外海种为主;优势种特征表现为种类数多而各个优势种丰度较低;浮游动物群落结构特征与南海北部海域浮游动物组成极为相似.     

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.