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”.     

Colonization of subtidal macroalgae in a fucalean-dominated algal assemblage,southwestern Australia

The influence of fucalean canopy species and dominant understory macroalgae on algal colonization was investigated to evaluate whether layering contributes to patterns in algal diversity. Patterns in recruitment were compared among total-clearing, understory-removal, canopy-removal, and undisturbed plots (plot area = 0.25 m²), using a randomized block design in depths <10 m and 10–20 m at Woody Island, Western Australia. To evaluate if propagules were available in the water column above the canopy layer, settlement plates (plate area = 0.04 m²) were deployed in depths <10 m, 10–20 m, and >20 m. A total of 198 macroalgal species was recorded. Biomass of the understory species Osmundaria prolifera Lamouroux and Botryocladia sonderi Silva was similar between canopy-removal and undisturbed plots. Diversity of macroalgae was similar in the presence and absence of a canopy layer. Taxa found in the canopy showed different patterns in recruitment. Cystoseiraceae recruited predominantly in total-clearings in both depth strata. Sargassaceae recruited most abundantly in depths <10 m. Density of canopy taxa on settlement plates was similar with depth (20–30 juveniles per plate), and juveniles were mainly Cystoseiraceae. In contrast to kelp beds or forests, patterns in algal colonization appeared to be maintained by environmental factors or processes other than the direct effects of layering in the subtidal fucoid-dominated assemblages at Woody Island. Handling editor: K. Martens     

Scales of spatial patterns of distribution of intertidal invertebrates

Few comparative studies of spatial patterns at different scales have examined several species in the same habitat or the same species over a range of habitats. Therefore, variability in patterns among species or among habitats has seldom been documented. This study quantifies spatial patterns of a suite of intertidal snails and a species of barnacle using a range of statistical techniques. Variability in densities was quantified from the scale of adjacent quadrats (over a distance of centimeters) to tens of kilometers. Significant differences in abundances occurred primarily at two spatial scales. Small-scale differences were found at the scales of centimeters or 1–2 m and, for many species on many shores, these accounted for most of the variability in abundances from place to place. These are likely to be determined by behavioural responses to small-scale patches of microhabitat. Large-scale differences in abundance were also found in most species at the scale of hundreds of meters alongshore. These are likely to be due to variation in recruitment (and/or mortality) because of limited dispersal by adults of these species. There was little or no additional variation among shores, separated by tens of kilometers, than was shown among patches of shore separated by hundreds of meters. Identification of the scale(s) at which significant differences in abundance are found focus attention on the processes (and the scales at which these processes operate) that influence patterns of distribution and abundance. Some of the advantages and disadvantages of various procedures are discussed.     

The significance of spatial and temporal patterns of algal mat deposition in structuring salt marsh vegetation

Question: Are there hot spots of algal mat deposition in space and time at the marsh scale and, if so, how does this affect the coexistence of a dominant (Spartina anglica) and gap dependent (Salicornia europaea) species? Location: The Rattekaai salt marsh in the Scheldt estuary in the southwestern Netherlands (NW Europe). Methods: Mat cover and the abundance of the gap dependent species Salicornia europaea were monitored at the scale of a marsh. The effects of mat cover on the vegetation structure were studied by applying three mat removal treatments over three growing seasons. Results: The low marsh border was found to be a hot spot of algal mat deposition during the growing season, which had a correlated spatial pattern between two successive years at a 20 m X 20 m scale. The combination of duration, timing and repetition of mat cover determined growth inhibition of the competitive dominant Spartina anglica, and thereby the abundance of subordinates such as Salicornia europaea. Mat cover reduced the storage of carbon reserves in Spartina and our results imply that repetition of non‐lethal mat cover can lead to ‘gap creation’. Gaps gave only temporary habitat to less dominant species since Spartina quickly re‐invaded them. The gap dependent annual Salicornia was most abundant at intermediate levels of disturbance measured as a function of both space and time. Conclusions In addition to disturbance level, the spatial and temporal distribution of disturbance are important in creating and maintaining habitat for gap dependent species. Relatively small disturbances will have a large effect on diversity if the spatial and temporal distribution of the disturbances leads to ‘disturbance hot spots’.     

Effects of live coral,epilithic algal communities and substrate type on algal recruitment

The recruitment of algae is a critical process during algal colonization and invasions, including coral-to-algal phase shifts. Although algae are widely assumed to colonize and kill corals, there is very little known about the recruitment dynamics of coral reef algae. This study tested the ability of two dominant macroalgae (Fucales including Sargassum spp. and Lobophora variegata) to settle and grow on healthy coral tissue. The study also explored the effects of interactions with prior occupants, and of abiotic substrate properties (texture, and ceramic and carbonate material). The results indicate that healthy corals were able to prevent attachment or survival of recruits of these macroalgae. This is a significant point, since it suggests that the replacement of corals by algae may often require prior stress or death in the coral tissue. Pre-conditioning of plates at different sites had some effects, but these were relatively minor, whereas there was considerable variation within sites. Some of this variation appeared to be related to the amount of turf algae or crustose coralline algae on the plates. Recruitment was generally, but not always, higher on plates with rougher texture. Overall, this preliminary exploration indicates considerable potential for variability in outcomes of algal colonization, with implications for the dynamics of algal invasions. In particular, the results do not support suggestions that planktonic algal propagules can directly settle on and colonize healthy coral tissue.Communicated by Topic Editor D. Barnes     

Effects of zinc on microalgal biofilms in intertidal and subtidal habitats

Microalgal biofilms are sensitive to environmental conditions. Impacts of contaminants on assemblages of marine biofilm are often investigated in laboratories or in mesocosms. Such experiments are rarely representative of the effects of contaminants on biofilms under natural conditions. Studies in field situations, with enough power to detect impacts, are necessary to develop a better understanding of the effects of contaminants on ecological processes. Metals are a common contaminant of marine systems and can cause disturbances to assemblages. Using a new technique to experimentally deliver contaminants to microalgal assemblages, hypotheses were tested regarding the effects of zinc on microalgal biofilms growing on settlement panels in subtidal and intertidal habitats. PAM fluorometry was used to assess the amount and physiological state of biofilms on panels. Control panels deployed for 1 month in each habitat had significantly greater amounts of biofilm than those exposed to zinc. After deployment for 3 months, the results varied with location. The observed effects on the biofilm did not, however, cause significant changes in the macro-invertebrate assemblages that developed on the panels.     

Biogeographical patterns of algal communities in the Mediterranean Sea: Cystoseira crinita‐dominated assemblages as a case study

Aim The aim of this study was to describe the composition, community structure and biogeographical variation of subtidal algal assemblages dominated by the brown alga Cystoseira crinita across the Mediterranean Sea. Location The Mediterranean coast, from Spain (1°25′ E) to Turkey (30°26′ E). Methods Data on the species composition and structure of assemblages dominated by the species C. crinita were collected from 101 sites in nine regions across the Mediterranean Sea. Multivariate and univariate statistical tools were used to investigate patterns of variation in the composition of the assemblages among sites and regions, and to compare these with previously defined biogeographical regions. Linear regressions of species richness versus longitude and versus latitude were also carried out to test previously formulated hypotheses of biodiversity gradients in the Mediterranean Sea. Results The main features characterizing C. crinita‐dominated assemblages across the Mediterranean included a similar total cover of species, a similar cover of C. crinita, and consistency in the presence of the epiphyte Haliptilon virgatum. Biogeographical variation was detected as shifts in relative abundances of species among regions, partly coinciding with previously described biogeographical sectors. A significant positive correlation was found between species richness and latitude, while no significant correlation was detected between species richness and longitude. Main conclusions The patterns of variation in community structure detected among the studied regions reflected their geographical positions quite well. However, latitude seemed to contribute more to the explanation of biological patterns of diversity than did geographical distances or boundaries, which classically have been used to delimit biogeographical sectors. Moreover, the positive correlation between species richness and latitude reinforced the idea that latitude, and possibly temperature as a related environmental factor, plays a primary role in structuring biogeographical patterns in the Mediterranean Sea. The lack of correlation between species richness and longitude contradicts the notion that there is a decrease in species richness from west to east in the Mediterranean, following the direction of species colonization from the Atlantic.     

Twenty-five years of change in coral coverage on a hurricane impacted reef in Hawai‘i: the importance of recruitment

Coral coverage was monitored 1981–2005 using a high precision method at four sites near Kahe Point, leeward O‘ahu, Hawai‘i by annually photographing ten 0.66 m² permanent plots at each site. The study began after a local storm reduced coral coverage in the area by about 50% in 1980 and included two major hurricanes in 1982 and 1992. Repeated measures ANOVA indicate significant differences among sites, time, and site-time interaction with high statistical power. Temporal changes in coral cover varied substantially among the sites, with the most stable coral coverage occurring near a thermal outfall. Although immediate impacts from hurricanes were not substantial, long-term decreases in coral coverage occurred well after the hurricanes. However, no relationships were found between coral cover and offshore wave conditions. Patterns of decline and recovery in coral cover were cyclic on a decadal time scale and significantly correlated with species and site-specific recruitment intervals of 10–12 years for Pocillopora meandrina and 15+ years for Porites lobata. Patterns indicated the potential importance of recruitment as a major factor affecting changes in coral coverage.     

Patchy recruitment patterns in marine invertebrates: a spatial test of the density-dependent hypothesis in the bivalve Spisula ovalis

Density-dependent and density-independent processes have been shown to influence the population dynamics of marine invertebrates, especially recruitment. However, their relative importance has not been evaluated in natural populations. High adult densities have been suggested to inhibit recruitment, especially in suspension-feeders which may ingest incoming larvae. Age structure and juvenile abundance were investigated in the bivalve Spisula ovalis in order to evaluate the importance of density dependence in generating spatial patterns. Age structure is readily established in this species owing to annual shell lines. An extensive sample (from about 100 sites a few hundred meters apart over 4 consecutive years) was analyzed in the statistical framework of spatial analyses, avoiding spurious correlations due to non-independence between neighboring sites. The area studied supports about ten annual cohorts, though only a few occur at each site. The overall picture is a mosaic of kilometer-scale patches of contrasted age structures, as revealed by highly significant spatial autocorrelations. To our knowledge, such large-scale spatial patterns in age structure have not previously been described in benthic invertebrates. Strong patterns are detected even for juveniles, and are independent of the adult biomass present before settlement. Therefore, patchy patterns of age structure mainly reflect density-independent effects, such as spatial variations in larval supply, passive transport of juveniles, or predation on recruits. In the absence of detailed spatial analyses, such patterns have been misinterpreted previously as negative effects of adult density on settlement success. Received: 21 November 1996 / Accepted: 20 February 1997     

Dispersal and recruitment of a canopy-forming intertidal alga: the relative roles of propagule availability and post-settlement processes

The daily settlement of eggs and zygotes of the monoecious brown alga Pelvetia compressa (J. Agardh) De Toni was measured on artificial substrata in areas inside and outside patches of adults in the high intertidal zone of central California. Settlement was generally 1–2 orders of magnitude higher under the adult canopy. This pattern seems to be due to the synchronous release of gametes during the daytime low tide. The release of gametes also appears periodic over longer time scales (e.g., 3- and 14-day cycles). In spite of the high availability of propagules under the adult canopy, juveniles were most abundant outside patches, where propagule availability was lower. In both areas, juveniles were disproportionately associated with patches of a red algal turf [primarily Endocladia muricata (Postels & Ruprecht) J. Agardh and Masticarpus papillata (C. Agardh) Kützing]. The turf, which is less common under the P. compressa canopy, may offer protection from dislodgment, grazing, and/or desiccation and thus facilitate recruitment at this site. Overall, post-settlement processes appear more important in determining population structure than does the availability of propagules in areas in and around patches of adults. However, the apparent small range of dispersal of P. compressa may make propagule availability an important limitation to the establishment of new populations and may restrict gene flow between populations. Received: 31 October 1997 / Accepted: 31 August 1998     

The role of fire in structuring trait variability in Neotropical savannas

Intraspecific trait variability plays a fundamental role in community structure and dynamics; however, few studies have evaluated its relative importance to the overall response of communities to environmental pressures. Since fire is considered a key factor in Neotropical savannas, we investigated to what extent the functional effects of fire in a Brazilian savanna occurs via intra- or interspecific trait variability. We sampled 12 traits in communities subjected to three fire regimes in the last 12 years: annual, biennial, and protected. To evaluate fire’s relative effects, we fitted a general linear mixed models with species as random and fire as fixed factors, using: (1) all species in the communities (i.e., considering intra- and interspecific variabilities); (2) 18 species common to all fire regimes (i.e., intraspecific variability only); and (3) all species with their overall average trait values (i.e., interspecific variability only). We assessed the relative role of intra- or interspecific variability by comparing the significance of each trait in the three analyses. We also compared the within and between fire variabilities with a variance component analysis. Five traits presented larger intraspecific than interspecific variability, and the main effect of fire occurred at the intraspecific level. These results confirm that it is important to consider intraspecific variability to fully understand fire-prone communities. Moreover, trait variability was larger within than among fire regimes. Thus, fire may act more as an external filter, preventing some of the species from the regional pool from colonizing the cerrado, than as an internal factor structuring the already filtered cerrado communities.     

The role of salinity in structuring the fish assemblages in a tropical estuary

The present study describes the seasonal changes of the fish species composition in three areas of the main channel of the Caeté River estuary, Brazil. The fish faunas of each habitat differed in density, biomass and species composition. Mean fish density and biomass for the Caeté River estuary channel was 0·25 individuals m⁻² and 0·9 g m⁻² respectively. Analysis of catch data showed that the number of species, total density and total biomass differed significantly between areas and seasons. For the most important species, the mean density of Cathorops spixii, Aspredinichthys filamentosus, Aspredo sp. 2, Pimelodus blochii, Pseudauchnipterus nodosus and Macrodon ancylodon , differed significantly between seasons while the mean density of Stellifer rastrifer , Stellifer microps, Aspredo aspredo , Aspredo sp. 1 and Cynoscion acoupa did not. The mean biomass of these species, with exception of S. microps and Aspredo sp. 1, also differed significantly between seasons. In the Caeté estuary seasonal salinity fluctuations appeared to be the main factor that structured the fish assemblage in the entire estuarine system. At least 85% of the species captured by the artisanal and subsistence fisheries in the Bragantine region required estuarine conditions to complete their life cycle.     

An integrated study of the temporal and spatial variation in the supply of propagules, recruitment and assemblages of intertidal macroalgae on a wave-exposed rocky coast, Victoria, Australia

Recruitment is known to influence distributions and abundances of benthic marine organisms. It is therefore important to document patterns of variability in recruitment and how these relate to patterns in established assemblages. This study provides an integrated assessment of the temporal and spatial variation in supply and recruitment of propagules and established populations of several macroalgae. Propagules in water samples from two stages of the incoming tide, recruitment to artificial substrata and percentage cover of species established on the shore were recorded every 2 months from December 1994 to October 1995, in two zones of an intertidal, wave-exposed rocky shore. Variability in recruitment was measured at three spatial scales: 10s cm, 100s cm and 100s m. Availability and recruitment of most taxa were greatest between April and August, although many species had available propagules and recruited throughout the year. Temporal variation in the established assemblages was, however, more species-specific. Differences in established assemblages between zones were reflected in differences in availability and recruitment of propagules between zones. Recruitment could not be predicted directly from supply of propagules, but the two processes were linked. For most species, the greatest variation in recruitment occurred at the smallest spatial scale of 10s cm, although there was also considerable large-scale (between site) variation in recruitment of several species. Results indicate that while pre-and post-settlement mortality are likely to influence macroalgal distribution and abundance, the temporal and spatial variability in supply and recruitment of propagules can explain much of the patchiness in macroalgal assemblages.     

Spatio-temporal variability of coral recruitment on shallow reefs in St. John, US Virgin Islands

In this study, coral recruitment was measured on a kilometer-wide scale over two years on shallow (5-6 m depth) fringing reefs in St. John, US Virgin Islands, with the objective of determining the extent to which variation in recruitment was affected by biophysical coupling involving temperature and flow. Coral recruitment was measured using settlement tiles deployed at 10 sites along 10 km of shore. The tiles were first deployed in August 2006, and thereafter replaced every ≈ 6 months to sample from either August to January, or January to August over 2 years. Seawater temperature was recorded at the 10 sites using logging thermistors, and flow was quantified using drogues. Overall, corals recruited at a rate equivalent to 76 corals m^− 2 6 months^− 1, and were represented mostly by poritids (43% of recruits), agaricids (29%), faviids (17%) and siderastreids (7%). Although the density of recruits differed among sites in a pattern that varied among periods and years, there was a consistent trend for mean density to decline from ≈ 4 corals tile^− 1 at eastern sites, to ≤ 1 coral tile^− 1 at western sites. One aspect of seawater temperature - the daily range - differed among sites and was greater at western compared to eastern sites, and while it was related inversely to recruitment over one of the sampling periods, it was equivocal as a physical process affecting recruitment. Instead, our results are consistent with biophysical coupling involving patch depletion and downstream filtering, whereby patches of coral larvae are delivered to the south shore of St. John and depleted of larvae through settlement as the water progresses westward.     

The influence of coastal topography, circulation patterns, and rafting in structuring populations of an intertidal alga

Understanding the dispersal processes that influence genetic structure in marine species requires estimating gene flow in a dynamic, fluid environment that is often poorly characterized at scales relevant to multiple dispersive stages (e.g. spores, gametes, zygotes, larvae, adults). We examine genetic structure in the marine alga Fucus vesiculosus L., which inhabits moderately exposed shores in the northern Atlantic but releases gametes only under sunny, calm conditions. We predicted genetic structure would correlate with coastal topography because weather frequently varies across coastal promontories on the Maine shore when F. vesiculosus is reproductive, which causes one side to experience high levels of water motion (= no gamete release) while one side is calm (= gamete release). Furthermore, we expected that the effect of low dispersal capacities of gametes and zygotes would result in spatial genetic structure over short distances. Using surface drifters, we characterized near-shore circulation patterns around the study sites to investigate whether directionality of gene flow was correlated with directionality of currents. We found significant genetic differentiation among sites sampled at two different peninsulas, but patterns of differentiation were unrelated to coastal topography and there was no within-site spatial structuring. Our genetic and near-shore circulation data, combined with an examination of gamete longevity, support the dependency of gene flow on storm-detached, rafting, reproductive adults. This study highlights the significance of rafting as a mechanism for structuring established populations of macroalgae and associated biota and demonstrates the importance of coupling population genetics' research with relevant hydrodynamic studies.     

Seasonal changes in an intertidal annual algal assemblage in northern Japan: The role of pre-emption and grazing on algal replacement

The pattern and process of seasonal changes in an intertidal annual algal assemblage were examined at Hiura, northern Japan. Short-term field experiments (<2months duration) were set up to quantify the effects of both grazing and pre-emption on species replacement in the assemblage in three different seasons. An 8-month field experiment was set up to quantify long-term effects, including the indirect effects of both grazing and competitive dominance on the community structure. Results suggested that seasonal change in the algal assemblage resulted from the interaction of abiotic environmental change, competition and grazing. The relative contribution of these factors varied within a short period, presumably as a result of seasonal changes in physical environmental stress, free space availability and grazing pressure. From February to March, when grazer density was low and there was much free space available for algae, the dominant species shifted from foliose green alga Monostroma angicava to filamentous red alga Bangia atropurpurea, because B.atropurpurea grew faster than M.angicava. This species replacement was not influenced strongly by biological interaction but by temporal changes in abiotic environmental conditions. From April to mid May, when there was less free space available for algae in the natural community, the dominant B.atropurpurea decreased with increasing foliose red alga Porphyra yezoensis, because only P.yezoensis was able to invade an area pre-empted by algae. Grazing did not affect this species replacement. After mid May, the two dominant species, P.yezoensis and B.atropurpurea, decreased. Their decline was mainly caused by desiccation stress and was partially affected by grazing.     

Habitat structure,conspecific presence and spatial variation in the recruitment of a temperate reef fish

Pronounced spatial variation in recruitment occurs in many marine invertebrate and fish populations and is thought to be critical to the demography of these species. In this study I examined the importance of habitat structure and the presence of conspecific residents to spatial variation in larval settlement and recruitment in a temperate fish Tautogolabrus adspersus. I define settlement as the movement of individuals from the water column to the benthic habitat, while I refer to recruitment as numbers of individuals surviving some arbitrary period of time after settlement. Experiments in which standard habitats were stocked with conspecifics showed that resident conspecifics were not an important factor contributing to small-scale variability in recruitment. Further correlative analyses demonstrated that large-scale variation in recruitment could not be explained by variability in older age classes. By contrast, manipulations of macroalgal structure within a kelp bed demonstrated that recruitment was significantly higher in habitats with a dense understory of foliose and filamentous algae than in habitats with only crustose algae. Understory algae varied in their pattern of disperison among sites, and the dispersion of fish matched that of the plants. In order to determine the effects of differences in patterns of algal dispersion on the demography of associated T. adspersus populations, I used experimental habitat units to manipulate patterns of dispersion. Settlement was significantly greater to randomly placed versus clumped habitats; however, no differences in recruitment between random and clumped habitats were detected. Because recruitment is a function of the numbers of settlers minus the subsequent loss of settlers, rates of mortality or migration must have been higher in the randomly placed habitats. These results are counter to the current paradigm for reef fishes which suggests that larval settlement is the crucial demographic process producing variability in population abundance. In this experiment patterns of settlement were modified by varying the patch structure of the habitat.Contribution number 278 from the Center for Marine Biology, University of New Hampshire     

Temporal and spatial patterns in emergence and early survival of perennial plants in the Sonoran Desert

Seedling emergence and survival of 15 perennial species were studied for six years in a 557-m² permanent plot at Tumamoc Hill, Arizona, USA, an ungrazed site in the northern Sonoran Desert. The minimum rain required for germination and emergence ranged from 17.5 to 35.6 mm. Few species emerged in every year of the study. First-year survival averaged across all 15 species was 3.7%; only 0.1% of seedlings lived as long as four years. The odds of survival in the first year improved with increased rain. About three times as many seedlings died from predation as desiccation. In 2-m² subplots, mortality of three woody species in the first 30 days after emergence appeared to be independent of seedling density. Short-, moderate-, and long-lived species displayed distinct survival strategies. Long-lived species compensated for generally poor seedling survival by frequent germination and emergence. Moderate-lived species exhibited highly episodic germination and emergence, a potentially risky behavior that might have been offset to some extent by relatively good long-term survival. Short-lived species had the highest seedling survival. Because these species can bloom in their first year, good early survival meant that some individuals were able to reproduce before they died.     

Spatial and temporal patterns in the recruitment of the intertidal barnacle Chthamalus malayensis Pilsbry (Crustacea: Cirripedia) on the equatorial shores of Peninsular Malaysia and Singapore

Spatial and temporal variation in the recruitment of the intertidal barnacle Chthamalus malayensis was examined over one year (September 2003-August 2004) on the equatorial shores of southern Peninsular Malaysia and Singapore. A nested sampling design was applied for the first time on these shores, over three spatial scales - hundreds of kilometres, kilometres to tens of kilometres and tens of metres - and temporal variation was determined through monthly sampling of recruits. Shores within 2° north of the equator on the East and West coasts of southern Peninsular Malaysia and the southern coast of Singapore were selected as study sites. Generally, all three coasts recruited throughout the year, with varying intensities. There was a clear regional pattern, where the largest number of recruits was found on the East Coast of Malaysia, and the least in Singapore. Analyses of variance (ANOVA) showed that variability occurred on the smallest scale, but only in nine of the twelve months examined, consequently resulting in significant temporal and spatial interaction. Calculated variance components indicated that small-scale variation accounted for most of the overall variability. The potential causes of the spatial and temporal patterns of C. malayensis recruitment, and implications on tropical-temperate comparisons will be discussed.     

Temporal and spatial patterns in ichthyoplankton assemblages in bay and open coastal environments

The larval fish fauna occurring in temperate bay and shelf waters off Victoria, southern Australia, was found to be diverse, comprising taxa from 52 families. The most abundant groups collected were gobiids, tripterygiids, gobiesocids and clupeids. Fish egg concentrations were highest during spring and summer (September to February). Eggs of the Australian anchovy Engraulis australis occurred mainly during spring (September to November). Total larval fish concentrations were highest during summer (December to February), and were significantly higher at 1 km than 2 and 5 km from shore in offshore samples. Larval concentrations of a number of families, mainly reef‐associated taxa that attach their eggs to hard substrata, were also higher nearer to shore. These larvae are more developed upon hatching than those of pelagic spawners and more capable of avoiding passive drift. Multivariate analyses found that larval taxonomic composition did not vary significantly with distance from shore, but that seasonal and monthly groupings were evident, with different taxa dominating at different times of the year. Larvae of the families Gobiidae and Tripterygiidae occurred in all months, but were less abundant during winter. Spatial differences in the larval fish assemblage between offshore samples and samples taken in the bay were only apparent during summer. This was primarily due to a higher abundance of seagrass‐associated species, such as syngnathids and hemiramphids, utilizing specific habitats in the bay.