Polychaetes of Truncated Reef Limestone Substrates on Eastern Indian Ocean Coral Reefs: Diversity,Abundance, and Taxonomy

This study provides the first evaluation of abundance and diversity of polychaete annelid assemblages of coral reefs. Quantitative analyses of the polychaete fauna of truncated coral reef limestone platforms off Sumatra and Thailand revealed a total of 76 species (13 reported for the first time from the tropical Indian Ocean) and average population densities of 49,000/m². The number of species in a single sample ranged from 16 to 32, and species diversity (H) ranged from 1.9 to 2.5. Three species of Syllidae, Palola siciliensis, and Dodecaceria laddi occurred in all samples. The syllids dominated numerically in all samples but were quite small, mainly 2–10 mm long and 0.01–0.04 mg dry weight. Samples from the same station were essentially identical in species composition and relative abundance. Similarity decreased with increasing distance between stations. With respect to number of species, population density, and dominance of syllids, the assemblages studied resemble those associated with limestone substrates in marine caves in the Mediterranean.     

Predation on reef-building corals: multiscale variation in the density of three corallivorous gastropods, Drupella spp.

 Feeding aggregations of three corallivorous gastropods, Drupella cornus, D. fragum and D. rugosa, have caused considerable coral damage on reefs across the Indo-West Pacific. Distribution and abundance of these three species were explored at Lizard Island, Great Barrier Reef, to determine within-reef variations in density, and spatial relationships between Drupella and their prey corals. The scales of greatest variation were between reef habitats (combinations of exposure and depth) and individual coral colonies. Density varied 12-fold among four habitats: exposed crests (2.55/m²), exposed slopes (0.22/m²), sheltered crests (0.34/m²) and sheltered slopes (2.07/m²). Species composition also varied markedly between habitats. Individuals were highly aggregated, usually forming small clusters (<10 individuals) on live coral colonies and other substrata, and occasional large aggregations of=200 to>2000. Five basic tenets for sampling Drupella are established, based on patterns of variation in density and species composition, and small-scale habitat use. Accepted: 8 February 1999     

Configuration of small patch reefs and population abundance of a resident reef fish in a complex coral reef landscape

Habitat use by the resident coral reef anemonefish, Amphiprion frenatus, was examined in the complex coral reef landscape of Shiraho Reef, Ishigaki Island, Okinawa, Japan, using an enlarged color aerial photograph processed using image analysis software as an accurate field map. The anemonefish inhabit assemblages of the host sea anemone, Entacmaea quadricolor (clonal type), which inhabit various patch reefs in the back reef moat. We located all patch reefs inhabited by the host in the map based on snorkel observations: 297 anemonefish were found in 93 host assemblages in the study site of 2.9 ha. These patch reefs could be recognized by the reef colors, including the shadows (blackish color) in the photograph. Using image analysis software, the colors of the patch reefs were chosen and pixels with the same color values were regarded as potential habitat patches for the fish (PHPs). PHPs were 3D patch reefs (>0.5 m in height). Total areas (TA) and total perimeters (TP) of PHPs were measured in nine quadrats in the digitized aerial photograph. Host abundance and anemonefish abundance in a quadrat showed stronger correlations with the product of TA and TP of PHPs than TA alone. A site with numerous large 3D patch reefs (≥0.75 m² in situ) can be a better habitat for the fish than other sites consisting of several huge 3D patch reefs of the same total area. The methodology applied here may be useful for assessing the quality of habitats for small resident animals in shallow subtidal reefs.     

Coral assemblages, biofacies, and ecological zones in the mid-Holocene reef deDosits of the Enriquillo Valley, Dominican Republic

Stemann, T. A. & Johnson, K. G. 1992 07 15: Coral assemblages, biofacies. and ecological zones in the mid-Holocene reef deposits of the Enriquillo Valley, Dominican Republic. A large, subaerially exposed mid-Holocene reef in the Enriquillo Valley (southwest Dominican Republic) provides an excellent opportunity to examine the relationship between reefal ecology and reefal deposits. Coral species richness and diversity in the Enriquillo reef are comparable to that found in the recent of the Caribbean, and ecological zonation comprised of a shallow-water branching coral zone and a deeper water mixed-coral zone is apparent. Similar zonation and diversity patterns have been recognized on living Caribbcan reefs with moderate wave exposure. Three statistically discrete biopdcies can be discriminated in the Enriquillo deposits using quadrat point-counting techniques commonly used to census modern reefs. They include a facies dominated by Acropora cervicornis, a low diversity assemblage with abundant, large colonies of Siderastrea siderea and Stephanocoenia intersepta, and a higher diversity assembbdge composed of various taxa including Montastraea spp., Colpophyllia spp., and Agaricia spp. Each facies can be recognized at scales of 1–3 m², though in some cases they extend for more than 20 m². In general, the A. cervicornis facies is spatially segregated from the other two biofacies. although neither the shallow nor the deep-water ecological zone is comprised of a single reef biofacies. Rather, the biofacies described here appear to represent distinct micro-environments resulting from ecological variation at a subzonal scale. Micro-environments of similar scale are most likely preserved in other reef deposits. Recognition of these subzonal biofacies may have important consequences for the stratigraphical and paleoccological interpretation of fossil reefs. Corals, biofacies, reef zonation, coral communities, fossil reefs.     

Ontogenetic shifts in the social behaviour of pairing coral reef rabbitfishes (Siganidae)

Adult rabbitfishes (Siganidae) differ from most other herbivorous coral reef fishes by forming stable pair bonds throughout their adult lives. However, little is known about the early life stages of rabbitfishes, and no quantitative evidence regarding the ontogeny of pairing behaviour exists to date. This study describes the abundance, distribution and ontogeny of social associations in juvenile rabbitfishes on the mid-shelf reefs around Lizard Island, Great Barrier Reef, Australia. Using underwater visual censuses, we surveyed an area of 5728?m² across three distinct habitat types, revealing that the abundance of juveniles varies significantly among species, size class and exposure level. Furthermore, we demonstrate a pronounced ontogenetic shift in the social associations of juveniles of Siganus doliatus and Siganus corallinus, changing from primarily solitary individuals in the smallest size class (<50?mm) to predominantly paired individuals in the larger size classes (50–100?mm and 100–150?mm). In this context, we report the presence of several mixed-species pairs of rabbitfishes, providing the first evidence for this behaviour within the family. This supports previous research, which posits that there are strong ecological drivers, rather than a solely reproductive basis, for pairing behaviour in rabbitfishes. Based on our results, we suggest that further exploration of the ecology of early life stages of herbivorous reef fishes will increase our knowledge about ecological processes on coral reefs.     

The structure of a nearshore fish community of Western Australia: diel patterns and the habitat role of limestone reefs

Synopsis Extensive limestone reefs are a characteristic feature of much of the coastline of Western Australia, and potentially represent a major habitat feature influencing the structure of the coastal fish community. The structure and temporal dynamics of the fish fauna and its relationships to nearshore patch reefs and surrounding habitat near Dongara, Western Australia, were examined using (1) diel gill-netting and (2) quantitative rotenone sampling of enclosed areas of substratum. Long-term and day-to-day variability of the fauna was low. Dominant species of gill-net collections were either associated with reefs or occurred in similar abundances at both reefs and surrounding sand/seagrass flats. The overall abundance, number of species and biomass of netted fishes was higher around reefs. Rotenone collections of the more sedentary species showed a similar pattern, but suggested, however, that a simple reef versus surrounding sand and seagrass habitat comparison is complicated by the canopy-forming seagrass Amphibolis that occurs on reef tops. Time of day had an important effect on overall fish abundance and number of species, with peaks occurring at crepuscular periods. This reflected dusk and dawn activity peaks of a dominant species rather than overlapping activities of many diurnal and nocturnal species. Diel switches between reef-edge habitat and surrounding sand/seagrass flats were uncommon despite expectations (based on literature examples) that patch reefs would function primarily as sheltering habitats and surrounding non-reef areas act as foraging habitat. High catches at reef-edge sites suggest that the majority of fishes forage on or near limestone patch reefs. Fish densities of around 0.8 individuals per m^-2 of bottom on these Western Australian reefs are relatively high in comparison to visual census estimates obtained for temperate reef systems in South Australia and New Zealand, but similar to those obtained using comparable netting methods in temperate Australian seagrass systems.     

Environmental factors influencing urchin spatial distributions on disturbed coral reefs (New Caledonia, South Pacific)

Few works have examined the relative contributions of habitat variables to the distribution of coral reef urchins. In the present study, the spatial distribution of two common urchin species (Diadema setosum and Echinometra mathaei) was studied in the fringing reefs of two urban bays in New Caledonia (South Pacific). Urchins were surveyed at 105 stations with contrasted habitat structure/anthropic disturbance levels; 32 environmental variables (water/sediment characteristics, reef structuring species) were considered. Moderate densities were generally observed at station scale (mean 0.5 individuals m^− 2). The combination of univariate and multivariate techniques highlighted patchy distributions for Diadema as well as Echinometra, with distinct species/habitat associations; environmental gradients occurring within the bays did not seem to influence the species patterns. For Diadema, the spatial variability was better explained by sediment type than by biotic cover; increasing densities occurred across habitats with larger sediment sizes and decreasing coral complexity/macrophytes cover. In contrast, the distribution of E. mathaei exhibited weak relationships with habitat variables. In coral reefs, small-scale heterogeneity may thus be responsible for most of urchins spatial variability.     

Maximal species richness in Conus: diversity, diet and habitat on reefs of northeast Papua New Guinea

The gastropod genus Conus is shown to be among many marine taxa that attain maximal known diversity along the northeast coast of Papua New Guinea. Thirty-six species co-occurred on the reef platform fringing Laing Island in Hansa Bay, 33% more than previously documented on any single reef. Near Madang, 32 species occurred on four small reefs. Maximal density at both sites was 3/m², with overall density 0.1-0.2/m². Species richness, diversity, and general patterns of microhabitat use were similar at both, but composition differed markedly. Only 23 species were found at both sites, and proportional similarity was 44%. The most common species at each site were uncommon at the other. The diets of 34 species were determined; 26, including the most abundant, preyed exclusively on polychaetes. As on other Indo-Pacific reefs, species partitioned prey types more finely than substrate types. Among vermivores, a different polychaete dominated the diet of each predator. Other species specialized on an enteropneust, other gastropods, and fishes. Most prey were herbivores or deposit feeders, indicating that the major trophic role of Conus species in the reef community is as primary carnivores. The results suggest that species are not more specialized than where fewer congeners co-occur, but rather overlap somewhat more in resource use.     

Density and height of Sargassum influence rabbitfish (f. Siganidae) settlement on inshore reef flats of the Great Barrier Reef

Macroalgal beds have been suggested to be an important settlement habitat for a diversity of reef fishes, yet few studies have considered how the composition or structure of macroalgal beds may influence fish settlement. The aim of this study was to investigate how the physical characteristics of Sargassum beds, a common macroalga on inshore coral reefs, influence the abundance of recently-settled rabbitfishes (Siganidae) on Orpheus Island, Great Barrier Reef. The abundance of recently-settled rabbitfish (< 3 cm total length), the density and height of Sargassum thalli, and benthic composition were quantified within replicate 1-m² quadrats across 15 mid-reef flat sites. A total of 419 recently-settled rabbitfish from three species (Siganus doliatus, S. lineatus and S. canaliculatus) were recorded across 150 quadrats (range 0–16 individuals m⁻²), with S. doliatus accounting for the majority (85.2%) of individuals recorded. The abundance of S. doliatus and S. lineatus was greatest at moderate Sargassum densities (ca. 20–30 holdfasts m⁻²) and generally increased with Sargassum height and the cover of ‘other’ macroalgae. These findings demonstrate the potential importance of the physical characteristics of macroalgal beds to the settlement of rabbitfishes on inshore reef flats.

     

河北唐山曹妃甸-乐亭海域自然牡蛎礁分布及生态意义

牡蛎礁是生态系统服务价值最高的海洋生境之一,目前我国自然牡蛎礁分布和生态现状的基础信息仍然较缺乏。于2019年3月对河北唐山曹妃甸-乐亭海域自然牡蛎礁的空间分布、生态环境、牡蛎生物学和礁体动物群落开展了调查,并评估了该牡蛎礁的生态系统服务价值。该海域自然牡蛎礁分布于溯河(SR)、溯河口海域(SRE)和捞鱼尖海域(LYJ),总面积约15 km~2,是目前我国面积最大的自然牡蛎礁。基于96个牡蛎样品的16S rDNA检测,共识别出92个长牡蛎Crassostrea gigas、3个侏儒牡蛎Nanostrea fluctigera和1个巨蛎属未知种Crassostrea sp.。自然牡蛎礁中牡蛎平均密度介于104—3912个/m~2之间,不同礁区间牡蛎平均密度的大小排序为：SRE>SR>LYJ (P<0.05),平均生物量的大小排序为：SR>SRE>LYJ (P<0.05),平均壳高的大小排序为：SR>SRE=LYJ (P<0.05)。在该牡蛎礁内记录到49种礁体动物,其中软体动物16种、节肢动物16种、环节动物8种、棘皮动物5种、腔肠动物2种...     

Non-native regal demoiselle,Neopomacentrus cyanomos,presence, abundance,and habitat factors in the North-Central Gulf of Mexico

Remotely operated vehicle (ROV) surveys were conducted at reef sites in the northern Gulf of Mexico (nGOM) during 2018–2019. Artificial (AR?=?63) and natural (NR?=?139) reefs were located in a 2?×?10⁵ km² area south of Mobile, AL to Destin, FL at depths of 13–75 m. We observed a total of 5371 damselfishes (Family: Pomacentridae) belonging to eight taxa. The non-native regal demoiselle (regal), Neopomacentrus cyanomos, was present at 30.2% of ARs but only 1.4% of NRs with densities ranging from 0.19 to 18.11 fish per 100 m². Regals were most dense at shallow ARs, comprising 53% of the damselfish community, and least dense at deeper reefs comprising?<?1% of observed damselfishes. Results from generalized linear mixed models (GLMMs) indicated the interaction among reef type, complexity, relief, and depth had a significant effect on regal density but that reef type (36%) and the interaction between reef type and depth (25%) explained the greatest proportions of variance in the data (partial η²) while the interaction among all four main effects explained only a small amount (2%). Our data indicate regals prefer shallow artificial structures with low complexity but can occupy deeper reefs, including NRs, despite less-favorable conditions. Our data document the persistence of regals in the nGOM and identify habitat factors that are significantly related to their presence and density in the region. However, the dynamics controlling their distribution are still uncertain and potential negative impacts on native reef fish communities remain unclear.

     

Oyster reef restoration: substrate suitability may depend on specific restoration goals

A limited supply of oyster shell for restoration practices has prompted investigations of alternative substrates used in construction of artificial oyster reefs. The success of oyster reef restoration projects is increasingly focused not only on oyster densities, but also on habitat provisioning for associated fauna. A subtidal oyster reef complex (0.24 km²) was restored in the Mission‐Aransas Estuary, Texas, U.S.A., in July 2013 using replicated mounds of concrete, limestone, river rock, and oyster shell substrates. Oyster and reef‐associated fauna characteristics were quantified quarterly for 15 months, using sampling trays that were deployed 3 months after construction. The highest densities of oyster spat occurred 9 months after tray deployment (July 2014, 1,264/m²), whereas juvenile oyster densities increased throughout the study period to 283/m². Concrete (1,022/m²) and limestone (939/m²) supported the highest number of oysters over all dates. Oyster shell (1,533/m²) and concrete (1,047/m²) substrates supported the highest densities of associated motile fauna. Faunal diversity (Hill's N1) did not vary by substrate material, but did show seasonal variation. A simple benefit–cost ratio was used to indicate the localized monetary value for each of the substrates. Oyster shell and concrete substrates returned the highest benefit–cost ratio for motile fauna, while concrete yielded the highest benefit–cost ratio for oyster abundance. Incorporating benefit–cost ratios in restoration planning will allow practitioners to better integrate substrate‐specific ecological values with economic considerations and project goals to maximize return on restoration investments.     

Maintenance of fish diversity on disturbed coral reefs

Habitat perturbations play a major role in shaping community structure; however, the elements of disturbance-related habitat change that affect diversity are not always apparent. This study examined the effects of habitat disturbances on species richness of coral reef fish assemblages using annual surveys of habitat and 210 fish species from 10 reefs on the Great Barrier Reef (GBR). Over a period of 11 years, major disturbances, including localised outbreaks of crown-of-thorns sea star (Acanthaster planci), severe storms or coral bleaching, resulted in coral decline of 46–96% in all the 10 reefs. Despite declines in coral cover, structural complexity of the reef framework was retained on five and species richness of coral reef fishes maintained on nine of the disturbed reefs. Extensive loss of coral resulted in localised declines of highly specialised coral-dependent species, but this loss of diversity was more than compensated for by increases in the number of species that feed on the epilithic algal matrix (EAM). A unimodal relationship between areal coral cover and species richness indicated species richness was greatest at approximately 20% coral cover declining by 3–4 species (6–8% of average richness) at higher and lower coral cover. Results revealed that declines in coral cover on reefs may have limited short-term impact on the diversity of coral reef fishes, though there may be fundamental changes in the community structure of fishes.     

Temperate macroalgae impacts tropical fish recruitment at forefronts of range expansion

Warming waters and changing ocean currents are increasing the supply of tropical fish larvae to temperature regions where they are exposed to novel habitats, namely temperate macroalgae and barren reefs. Here, we use underwater surveys on the temperate reefs of south-eastern (SE) Australia and western Japan (~33.5°N and S, respectively) to investigate how temperate macroalgal and non-macroalgal habitats influence recruitment success of a range of tropical fishes. We show that temperate macroalgae strongly affected recruitment of many tropical fish species in both regions and across three recruitment seasons in SE Australia. Densities and richness of recruiting tropical fishes, primarily planktivores and herbivores, were over seven times greater in non-macroalgal than macroalgal reef habitat. Species and trophic diversity (K-dominance) were also greater in non-macroalgal habitat. Temperate macroalgal cover was a stronger predictor of tropical fish assemblages than temperate fish assemblages, reef rugosities or wave exposure. Tropical fish richness, diversity and density were greater on barren reef than on reef dominated by turfing algae. One common species, the neon damselfish (Pomacentrus coelestis), chose non-macroalgal habitat over temperate macroalgae for settlement in an aquarium experiment. This study highlights that temperate macroalgae may partly account for spatial variation in recruitment success of many tropical fishes into higher latitudes. Hence, habitat composition of temperate reefs may need to be considered to accurately predict the geographic responses of many tropical fishes to climate change.

     

临海东矶海域人工鱼礁大型底栖动物群落的早期发育

为养护渔业资源和修复受损海岸带生态系统,人工鱼礁通常被投放至沿岸海域的海底,为海洋生物提供新的栖息地。于2022年5月(投放后10个月)和10月(投放后15个月)调查了临海东矶人工鱼礁大型底栖动物群落,分析了不同礁龄间大型底栖动物种类组成、密度、生物量和群落结构的差异。两次调查共记录到5类17种大型底栖动物,优势种为猫爪牡蛎Talonostrea talonata和侧花海葵Anthopleura sp.。礁体投放10个月后大型底栖动物群落的平均密度和平均生物量分别为(3519±289)个/m²和(3657±273)g/m²,15个月后平均密度和平均生物量分别为(10056±1858)个/m²和(8300±2045)g/m²,15个月的密度和生物量均显著高于10个月的(P>0.05)。不同礁龄间大型底栖动物群落结构具有显著性差异(Globe R=0.573, P=0.029),导致群落结构差异的物种主要是曲膝薮枝螅Obelia genicutata、侧花海葵、褐蚶Didimarca tenebricum、丽核螺Tritonoharpa leali、双纹须蚶Barbatia bistrigata和疣荔枝螺Thais clavigera。礁体投放10个月后和15个月后人工鱼礁附着猫爪牡蛎的平均密度分别为(2075±37)个/m²和(2194±397)个/m²,不同礁龄间没有显著性差异(P>0.05)。发现临海东矶人工鱼礁表面分布有低物种丰度和高密度的大型底栖动物群落,并发育成为以猫爪牡蛎为造礁种的人工牡蛎礁。     

Mass Mortality of Coral Reef Ascidians Following the 1997/1998 El Niño Event

In April/May each year from 1995 to 2000, ascidians were sampled randomly with 35 1m² quadrats from three different reef habitats (intertidal reef tops, coastal reef walls and shallow-bank reefs) at four replicate localities (Praia do Forte, Itacimirim, Guarajuba and Abai) in northern Bahia (Brazil). As the sampling period included the 1997/1998 El Niño event, the most severe on record, for the first time these results allow a quantitative assessment of the impact of this major environmental stressor on the biodiversity of associated coral reef ascidians. Across all reef habitats, 22 ascidian species were recorded from three different orders (Aplousobranchia, Phlebobranchia and Stolidobranchia). After El Niño, all species showed significantly altered densities (ANOVA, F=602.90, p<0.0001); many species were absent from the reefs within 2 years of the El Niño period, but densities of Lissoclinum perforatum (all reefs) and Echinoclinum verrilli (subtidal reefs) increased significantly from 1998 onwards. Univariate and multivariate analyses confirmed that significant changes in assemblage composition had occurred. BIOENV analysis identified turbidity, mean temperature and cloud cover as the main factors best explaining these assemblage changes. Our results suggest that although the 1997/1998 El Niño had a differential effect on the species contributing to the ascidian assemblage of Brazilian coral reefs, most species disappeared and those remaining are likely to enhance reef degradation through their bioeroding activities.     

Bottlenecks to coral recovery in the Seychelles

Processes that affect recovery of coral assemblages require investigation because coral reefs are experiencing a diverse array of more frequent disturbances. Potential bottlenecks to coral recovery include limited larval supply, low rates of settlement, and high mortality of new recruits or juvenile corals. We investigated spatial variation in local abundance of scleractinian corals in the Seychelles at three distinct life history stages (recruits, juveniles, and adults) on reefs with differing benthic conditions. Following widespread coral loss due to the 1998 bleaching event, some reefs are recovering (i.e., relatively high scleractinian coral cover: ‘coral-dominated’), some reefs have low cover of living macrobenthos and unconsolidated rubble substrates (‘rubble-dominated’), and some reefs have high cover of macroalgae (‘macroalgal-dominated’). Rates of coral recruitment to artificial settlement tiles were similar across all reef conditions, suggesting that larval supply does not explain differential coral recovery across the three reef types. However, acroporid recruits were absent on macroalgal-dominated reefs (0.0 ± 0.0 recruits tile^?1) in comparison to coral-dominated reefs (5.2 ± 1.6 recruits tile^?1). Juvenile coral colony density was significantly lower on macroalgal-dominated reefs (2.4 ± 1.1 colonies m^?2), compared to coral-dominated reefs (16.8 ± 2.4 m^?2) and rubble-dominated reefs (33.1 ± 7.3 m^?2), suggesting that macroalgal-dominated reefs have either a bottleneck to successful settlement on the natural substrates or a high post-settlement mortality bottleneck. Rubble-dominated reefs had very low cover of adult corals (10.0 ± 1.7 %) compared to coral-dominated reefs (33.4 ± 3.6 %) despite no statistical difference in their juvenile coral densities. A bottleneck caused by low juvenile colony survivorship on unconsolidated rubble-dominated reefs is possible, or alternatively, recruitment to rubble-dominated reefs has only recently begun. This study identified bottlenecks to recovery of coral assemblages that varied depending on post-disturbance habitat condition.     

Ecosystem engineering by a canopy‐forming kelp facilitates the recruitment of native oysters

Ecosystem engineers are species that influence the abiotic and biotic environment around them and may assist the restoration of associated species, including other habitat‐forming species. We deployed an array of 28 artificial reefs with transplanted Ecklonia radiata, the dominant canopy‐forming kelp species across southern Australia, to investigate how the patch size and density of E. radiata influenced the establishment of the associated communities of plants and animals. Many of the reefs were rapidly colonized by Ostrea angasi, a critically depleted reef‐forming oyster. Over the 24‐month deployment of the reefs, thick oyster mats formed across the entire surface of many of the reefs with estimated biomass densities exceeding 5 kg of live oysters/m²; however, oyster density was dependent on E. radiata patch size and density. Increasing patch size and the presence of kelp resulted in significantly higher densities of oysters 5 months after the reefs were deployed and at the end of the experiment, where oysters were approximately three times more numerous on reefs with kelp compared to those without kelp. E. radiata appeared to facilitate the establishment of O. angasi largely through its capacity to reduce benthic light and thus suppress competition from turfing algae. These results may inform the development of novel approaches to tackle recruitment bottlenecks affecting the restoration of O. angasi reefs.     

Forgotten underwater forests: The key role of fucoids on Australian temperate reefs

Kelp forests dominated by species of Laminariales are globally recognized as key habitats on subtidal temperate rocky reefs. Forests characterized by fucalean seaweed, in contrast, receive relatively less attention despite being abundant, ubiquitous, and ecologically important. Here, we review information on subtidal fucalean taxa of Australia's Great Southern Reef, with a focus on the three most abundant and widely distributed genera (Phyllospora, Scytothalia, and Sargassum) to reveal the functionally unique role of fucoids in temperate reef ecology. Fucalean species span the entire temperate coastline of Australia (~71,000 km²) and play an important role in supporting subtidal temperate biodiversity and economic values on rocky reefs as well as in adjacent habitats. Climatic and anthropogenic stressors have precipitated significant range retractions and declines in many fucoids, with critical implications for associated assemblages. Such losses are persistent and unlikely to be reversed naturally due to the life history of these species and colonization of competitors and grazers following loss. Active restoration is proving successful in bringing back some fucoid species (Phyllospora comosa) lost from urban shores and will complement other passive and active forms of conservation. Fucalean forests play a unique role on subtidal temperate reefs globally, especially in Australia, but are comparatively understudied. Addressing this knowledge gap will be critical for understanding, predicting, and mitigating extant and future loss of these underwater forests and the valuable ecosystem services they support.     

Subtidal and intertidal mussel beds (Mytilus edulis L.) in the Wadden Sea: diversity differences of associated epifauna

In 1997 and 1998, surveys were performed to compare species composition, abundance and diversity of non-attached epifauna (>1 mm) in low intertidal and adjacent shallow subtidal zones of three mussel beds (Mytilus edulis L.) near the island of Sylt in the North Sea. The community structure was similar when compared within tidal zones: no significant differences in species numbers and abundances were recorded between locations and between years. A comparison between tidal zones, however, revealed higher diversity, species densities and total species numbers in the subtidal (per 1,000 cm²: H ′=2.0±0.16; 12 ±1 species density; 22 species) than the intertidal zone (per 1,000 cm²: H ′=0.7±0.27; 6±2 species density; 19 species). Abundances significantly dropped with increasing submergence from 2,052 (±468) m^–2 to 1,184 (±475) m^–2. This was mainly due to significantly higher densities of both juvenile periwinkles, Littorina littorea, and crabs, Carcinus maenas, in intertidal mussel beds. However, many less dominant species were significantly more abundant in subtidal mussel beds. This study revealed that in the non-attached epifaunal community of mussel beds the tidal level effect within metres was strong, whilst the spatial variability in a much wider (kilometre) range but the same tidal level was negligible. The high epifaunal diversity in the subtidal zone suggests that the protective measures for mussel beds against the effects of mussel fishery should be extended from the intertidal to the subtidal zone, if the integrity of the mussel bed community in the Wadden Sea National Park is to be maintained. Electronic Publication