Underside Of Boulders Research Articles

Contrasting patterns of decadal stability for shallow water sponge boulder assemblages and subtidal rocky cliffs at Lough Hyne, Ireland

Abstract Lough Hyne (LH) Marine Nature Reserve in Ireland is a globally recognised biodiversity hotspot that hosts mesophotic-like communities in shallow water, however, major changes have occurred to most of the rocky cliff (>6 m) communities in one or more events between 2010 and 2015. To provide insights into these changes, we compared the sponge assemblage composition on the undersides of different sized, shallow (<1 m) subtidal boulders between 2000 and 2022 at two sites in LH. We also measured sponge species richness at seven sites in 2018. We found that unlike earlier reports from the deeper subtidal reef sponge assemblages, there was no evidence for changes in sponge assemblage composition on the undersides of boulders at either site. We also found high levels of sponge species richness at all seven sites sampled in 2018. We did find differences in sponge assemblages between sites and for different boulder sizes, which we propose is a result of site-specific environmental conditions and disturbance and size–area relationships. Since we found no changes in the shallow subtidal sponge assemblages between 2000 and 2022, our results support the hypothesis that changes to the deeper subtidal sponge assemblages at LH are driven by local processes associated with deeper water in LH, potentially related to the seasonal oxythermocline that forms within LH. Given the national and global importance of LH, understanding the drivers of change is critical to determine if management actions can prevent any future alterations to the LH sponge assemblages and support wider mesophotic community management.

Behavioural thermoregulation and food availability drive fine‐scale seasonal habitat partitioning in limpets

Abstract Small‐scale spatial variation in temperature plays a key role in limiting the distribution of organisms in thermally heterogeneous environments. In the rocky intertidal zone, intra‐day temperature variation at small scales (cm–m) can easily exceed 30°C. To experimentally test the impact of this small‐scale temperature heterogeneity on the distribution of an ecologically important limpet species (Cellana denticulata), boulders on an intertidal rocky reef in New Zealand were rotated and small‐scale temperature variability and food availability were measured throughout 1 year. Small‐scale variability in thermal tolerance, heart rate and heat shock protein expression was also measured to relate in situ limpet distributions with environmental conditions. Temperature variability was measured using limpet bio‐mimics and HOBO pendant temperature loggers, while food availability (chlorophyll a concentration) was measured on in situ concrete fibreboard tiles. To measure limpet distributions, every tagged limpet on each of 18 boulders was followed from June 2021 to 2022. During each sampling, the location of each limpet, compass direction and slope of the surface that each limpet inhabited was measured. To test for physiological differences among limpets from each microhabitat, thermal tolerance and heat shock protein expression were measured in collected limpets; in situ heart rates and body temperatures were also measured sporadically on hot days. Maximum predicted body temperatures (36–39°C), heart rates and actual body temperatures were greatest on equatorial surfaces (i.e. surfaces facing the equator) whereas food availability was greatest on poleward‐facing surfaces. During summer, limpets moved towards surfaces that minimised their body temperatures and maximised food availability, namely vertical and poleward‐facing surfaces and undersides of boulders. Thermal tolerance, measured using Arrhenius breakpoint temperatures (mean ± SE: 34.7–35.8 ± 0.4–0.7°C) and flat line temperatures (36.2–37.4 ± 0.3–0.4°C), was similar among limpets facing different directions. Surprisingly, heat shock protein expression was relatively consistent throughout the year and among directions. Overall, limpet populations are resilient to thermal stress because they effectively use behavioural thermoregulation to exploit cooler microhabitats that also have greater food availability during summer. Read the free Plain Language Summary for this article on the Journal blog.

Low temperature exposure determines performance and thermal microhabitat use in an intertidal gastropod (Littorina scutulata) during the winter

Small-scale spatial variation in temperature is an important attribute of many habitats, as spatial thermal refugia may allow organisms to avoid some negative consequences of thermal extremes. Although the ecological importance of thermal refugia in intertidal habitats is well-known in summer, the relative availability, effectiveness, and ecological relevance of thermally benign microhabitats in the winter is poorly understood. Here, we explored small-scale thermal variability on a temperate rocky coastline during winter, and the relevance of these thermal patterns to Littorina scutulata, a common intertidal gastropod. Sheltered microhabitats, including crevices, undersides of boulders, and areas beneath algal canopy, were all warmer than surrounding exposed areas during winter low tides. L. scutulata was able to recover relatively quickly from exposure to low temperatures down to -3°C, but performance costs began to accrue at lower temperatures. However, the presence of a refuge habitat buffered the negative effects of cold temperatures, and sheltered L. scutulata regained mobility more quickly than conspecifics on exposed surfaces. Further experiments demonstrated that L. scutulata were more frequently found in thermal refugia when previously exposed to low temperatures, but not when exposed to milder temperatures. Our results suggest that realistic low temperatures can impose important costs on intertidal species such as L. scutulata, but the availability of thermal refugia coupled with behavioural adaptations can allow species to reduce many such costs. Just as in summer, thermal refugia in winter may be important for the distribution and abundance of intertidal species and the diversity and function of coastal ecosystems.

Availability of microhabitats explains a widespread pattern and informs theory on ecological engineering of boulder reefs

The availability of suitable microhabitats has emerged as a key requirement for maximising species diversity gains from ecological engineering of coastal habitats. This includes intertidal boulder field habitat, which is threatened by increasing urbanisation. We examined faunal use of microhabitats offered by natural intertidal boulders on two continents, South Africa and Australia, and then used artificial boulders to test possible mechanisms driving the observed patterns. Gaps often occur between the undersides of boulders and the substratum on which they lie. Substrata underneath boulders are generally uneven, so gaps can occur anywhere along the boulder undersurface, but gaps are generally larger near the edges of naturally-occurring boulders. Boulder edges were found to provide a microhabitat that had greater densities of almost all macrofauna than closer to the centre of boulder undersides. To test the model that microhabitat use of boulder edges reflects their larger gap sizes (relative to boulder centres), artificial boulders were constructed with the underside surface either flat, or with a gap underneath mimicking the mean size of the gap normally found only under boulder edges (when their average shape is considered among numerous naturally-occurring boulders). Artificial boulders were deployed intertidally for seven weeks, and macrofaunal colonisation was compared (a) between flat boulders and those with gaps, and (b) between edges and centres. Five times more macrofauna colonised boulders with artificial gaps, while no effect of proximity to edges was found when the gap-width was controlled for. The size of gaps under boulders appears to be an important microhabitat feature that can explain a widespread distributional pattern in the diverse assemblages of boulder fields. Such gaps are clearly used by numerous species, including some that are rare or commercially important. Provision and augmentation of this microhabitat should be considered for any ecological engineering project that involves intertidal or subtidal boulders.

Hiding behaviour of Oxynoe olivacea (Mollusca: Opisthobranchia: Sacoglossa) in the invasive seaweed Caulerpa taxifolia

The occurrence of the invasive seaweed Caulerpa taxifolia in the Straits of Messina (Italy) provides an excellent opportunity to examine the spatial and temporal patterns of abundance of the endemic Mediterranean sacoglossan Oxynoe olivacea. Densities of this species were recorded in March, June and October 2000 on three different habitats: the underside of boulders (UNB), the upper side of boulders (UPB), and the surface of concrete blocks (CB). Results showed that in March, O. olivacea was consistently more abundant on UNB whereas in June it was present exclusively on CB. The density of O. olivacea was similar in the three habitats in October. The hiding behaviour of O. olivacea and its seeming disappearance in March did not coincide with a decline of abundance of phylloids of C. taxifolia. The results represent an important basis for further studies devoted to the investigation of abundance of these marine invertebrates, which has been traditionally thought of as unpredictable.

Physical and biological effects of introduced oysters on biodiversity in an intertidal boulder field

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 482:119-132 (2013) - DOI: https://doi.org/10.3354/meps10241 Physical and biological effects of introduced oysters on biodiversity in an intertidal boulder field Dannielle S. Green*, Tasman P. Crowe Marine Biodiversity, Ecology and Evolution group, School of Biology and Environmental Sciences, University College Dublin, Dublin 4, Ireland *Email: danniellesgreen@gmail.com ABSTRACT: Invasive species have been identified as a serious threat to biodiversity, particularly in protected habitats. The Pacific oyster Crassostrea gigas, which is invasive in many parts of the world, can form very dense populations affecting the abundance and distribution of native organisms. We experimentally separated the effects of the cover and state (physical structure or biological activities) of C. gigas on the development of invertebrate and macroalgal assemblages. Living (biologically active) and dead (physical structure only) oysters were glued in increasing cover to the tops of cleaned boulders and deployed within an intertidal boulder field. After 14 mo, diversity, evenness and assemblage structure of invertebrates and algae were affected by C. gigas, and results varied depending on the cover and state of oysters. Interestingly, boulders with the lowest cover of living C. gigas supported the most diverse assemblages. Differences in assemblage structure were driven by changes in the establishment of several key species including Fucus vesiculosus and Littorina littorea, which were facilitated by oysters and the honeycomb worm Sabellaria alveolata, which was inhibited by oysters. S. alveolata, an ecosystem engineer that can generate reefs protected by the European Union Habitats directive, mainly established on the underside of boulders but was nonetheless greatly reduced by increasing cover of dead or living oysters on the topside. This work highlights the importance of understanding the direct and indirect mechanisms by which invasive species alter biodiversity and how effects vary as invaders increase in abundance. KEY WORDS: Invasive species · Biodiversity · Protected habitats · Ecosystem engineer · Density dependent · Crassostrea gigas · Sabellaria alveolata Full text in pdf format PreviousNextCite this article as: Green DS, Crowe TP (2013) Physical and biological effects of introduced oysters on biodiversity in an intertidal boulder field. Mar Ecol Prog Ser 482:119-132. https://doi.org/10.3354/meps10241 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 482. Online publication date: May 22, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

Patterns of sponge biodiversity and abundance across different biogeographic regions

Few studies have compared the underlying nature or structure of marine communities and assemblages across broad spatial scales, despite the importance of such comparisons in understanding global scale responses to environmental change and biodiversity conservation. The aim of this study was to examine the consistency of relationships between sponge abundance and richness on the undersides of boulders (to control for multiple confounding factors) in relation to space availability (boulder size) in three widely separated biogeographic regions. Sponges followed typical species-area (SA) relationships irrespective of site or ocean and we consistently found no decrease in sponge richness at larger boulder sizes. We also found reliable underlying density–area (DA) relationships, with larger boulders supporting more sponge patches at all sites. Although the general SA and DA relationships were similar between oceans and sites, the exact nature of these relationships in terms of the actual species present per unit area, total number of species present or density differed between sites. There were no consistent differences between SA and DA relationships at each locality, suggesting that although disturbance (particularly wave action) regimes may play an important role in controlling sponge biodiversity and abundance, its effects are manifested differently at local-scales. Even though boulders have received a considerable amount of research effort over the past three decades, this is the first study to examine the consistency of DA and SA relationships between ocean basins, finding similar relationships.

Gastropod egg mass deposition on a temperate, wave‐exposed coastline in New South Wales, Australia: implications for intertidal conservation

Abstract The identification and protection of known breeding grounds is a high priority for the conservation of marine biodiversity. Here, we examine the intertidal habitats used by marine gastropods for the deposition of benthic egg masses along a wave‐exposed coastline in New South Wales, Australia. A total of 200 surveys were conducted on 13 intertidal reefs. The egg masses of 46 species were identified, with a further eight distinct types recorded but remaining unidentified. Over half of the gastropods were found to deposit egg masses exclusively on the underside of boulders. Other intertidal substrata used for gastropod egg mass deposition included vertical and horizontal exposed rock surfaces, algal fronds and sand. Only eight species were found to attach their egg masses to more than one type of substratum. Twelve reefs were classified into three categories according to exposure to wave action and habitat diversity. The mean number of species found depositing egg masses was compared using a standard eight surveys from each site. Sub‐maximally wave‐exposed reefs with maximal habitat diversity were found to support a significantly higher species richness of gastropod egg masses, compared with maximally wave‐exposed reefs with either maximal or sub‐maximal habitat diversity (p=0.000). Gastropods that deposit egg masses on the underside of boulders were more likely to be found on sub‐maximally wave‐exposed reefs, whereas species that deposit egg masses in all other microhabitats were equally likely to be found breeding on sub‐maximally or maximally exposed reefs. Gastropods with pelagic larvae tended to occur at a greater number of sites than those that hatch post‐metamorphosis. A significant difference was found between species grouped according to these two developmental modes for the mean number of sites at which egg masses were recorded (p=0.008). Variation in the species richness of gastropods found depositing egg masses on different intertidal reefs appears to be influenced by the availability of suitable boulders and exposure to wave action. These factors should be taken into consideration during the selection of locations for intertidal protected areas. Copyright © 2004 John Wiley & Sons, Ltd.

The North-American amphipods, Melita nitida Smith, 1873 and Incisocalliope aestuarius (Watling and Maurer, 1973) (Crustacea: Amphipoda: Gammaridea), introduced to the Western Scheldt estuary (The Netherlands)

The American amphipod species Melita nitida andIncisocalliope aestuarius have been found in the WesternScheldt estuary (the Netherlands). This is the first record of these species inthe north-east Atlantic. Shipping is the most likely vector of introduction.Thedistribution of both species is investigated and compared with the distributionand the microhabitat of co-occurring amphipod species. Melitanitida is known from both the east and west coast of North Americaand I. aestuarius originates from the east coast of NorthAmerica. Until now neither has been reported from other parts of the world. Inthe Netherlands both species are restricted to the mesohaline part of theWestern Scheldt. Melita nitida occurs predominantly underPacific oysters at the underside of boulders, mainly sublittorally.Incisocalliope aestuarius is associated to hydrozoans.Bothmicrohabitats are hardly utilized by other amphipod species. Therefore, thetheory that the existence of many empty niches in north-western Europeanbrackish waters make this environment particularly susceptible to invasions ofalien species is corroborated. The application of hard substrates in a regionoriginally predominated by soft bottoms moreover facilitates the introductionofexotic species. The species community on hard substrates in the mesohaline partof the Western Scheldt contains a high proportion of introduced species:approximately one third of the macrofauna species is of allochthonous origin.

Note on the Trophic Relationships of the Stauromedusa Haliclystus Antarcticus from Subantarctic South Georgia

Stauromedusae are cnidarians that have attracted relatively little ecological study, especially in the southern hemisphere. They are Scyphozoa that develop directly from the scyphistoma, and each consists of a calyx and a more or less distinct aboral peduncle that attaches to the substratum by an adhesive disc. The animals are mobile on the substratum, but have no pelagic phase. The present note originates from observations made on stauromedusae living in intertidal and shallow subtidal waters at Husvik Harbour, South Georgia (54°11′S 38°40′W) in early 1994. The species concerned was identified from Kramp (1961), Carlgren (1930) and Pfeffer (1889) as Haliclystus antarcticus Pfeffer, 1889. This species has attracted little previous study. The most detailed anatomical description was given by Carlgen (1930), while distributional details are given in O'Sullivan (1982) who followed Pfeffer (1889); at present there is no evidence that the species occurs other than at South Georgia.Medusae were found on two substrata. Large animals (~30mm high, inconspicuous dark brown in colour) were found on the underside of boulders at extreme low spring tide level in a bay on the north of Husvik Harbour about 1·2 km from the whaling station and close to Brain Island. Locally they were common, often being close enough to touch one another. Smaller animals (pink-orange in colour; cryptic on the macroalga) were found attached to the brown macroalga Desmarestia menziesii J. Aghardh (Phaeophyceae) collected at low-water spring tide level from Kanin Point on the southern shore of the harbour. Medusae on boulders were briefly emersed on particularly low tides: they collapsed, hanging from the peduncle, when out of water, but did not risk desiccation as their habitat was wet and not exposed to the sun.

Competition for Space in encrusting bryozoan assemblages: the influence of encounter angle, site and year

This field study examined competition for space among encrusting bryozoans on artificial panel substrata used to simulate the habitat found on the undersides of boulders. In all 1761 interactions were analysed, involving 16 species of cheilostomes (genera Callopora, Celleporella, Cribrilina, Electra, Escharella, Escharoides, Haplopoma, Membraniporella, Microporella, Phaeostachys, Schizomavella, Schizoporella and Umbonula) and two ctenostome genera (Alcyonidium and Flustrellidra). Neither absolutely transitive nor intransitive arrangements of competitive outcome occurred among the species. Instead, the high incidence of ‘ties’ and reversals of outcome produced a network-like arrangement. In terms of outcome alone Escharoides coccinea (Abildgaard), Membraniporella nitida (Johnston) and Schizoporella unicornis (Johnston in Wood) were apparently ‘overgrowth dominants’, Alcyonidium spp. and Cribrilina cryptooecium Norman were ‘intermediate dominants’ and Callopora lineata (L.), Callopora craticula (Alder), Celleporella hyalina (L.) and Electra pilosa (L.) were ‘inferior competitors’ for space. The effects of four variables on the outcome of specific competitive encounters were assessed in detail and included (i) the identity of the colony encountered, (ii) the angle of contact between the competing colonies, (iii) the location (two sites, on both the east and west coasts of Scotland) and (iv) the year (1983, 1984). Models incorporating these variables were developed, using the Generalized Linear Interactive Modelling System (GLIM), to examine their influence on the outcome of bryozoan encounters. All of these factors contributed to explaining the considerable variability in the outcome of competitive interactions. The species were not, however, affected equally by all the variables, although encounter angle and year were significant for dominants and encounter angle, site and year all were significant for intermediate species.

Responses of a Rocky Shore Gastropod to the Effluents of Predatory and Non-predatory Crabs: Avoidance and Attraction.

Laboratory experiments revealed that the rocky shore gastropod, Nucella lamellosa (Gmelin), could discriminate between the effluents of predatory and non-predatory crabs. N. lamellosa turned away from seawater that had passed over the large predatory crab, Cancer productus Randall. This avoidance behavior was observed in snails from two localities that, based on differences in shell form, presumably experienced different levels of predation intensity. The scent of the non-predatory crabs Pugettia producta (Randall) and Lopholithodes mandtii Brandt had no effect on the turning behavior of snails from either site. Surprisingly, snails from both sites were attracted to the scent of a small shore crab, Hemigrapsus nudus (Dana), but moved at random in response to a common prey item Balanus glandula Darwin. These results suggest that N. lamellosa can assess from a distance the relative risks posed by different species of crabs, and respond appropriately. The unexpected attraction to H. nudus suggests that N. lamellosa may use this effluent to home in from a distance on potential refugia, because H. nudus are often associated with crevices and the undersides of boulders where N. lamellosa would be less vulnerable to larger predators.

Ecological succession on cobble substrates: a reply

In a recent paper, Kobluk and Lysenko (1987) described the effects of hurricanes on coral and milleporid distribution in coral reef rubble near the coast of a Fijian island. Their main thesis was that cryptic sub-rubble coral populations may act as “preserves” for reef surface communities. This was supported by data showing that on the protected undersides of boulders the composition of post-hurricane coral and milleporid populations were little changed from their pre-hurricane states. In a final section entitled “Paleontological implications,” Kobluk and Lysenko (1987, p. 673) stated, “Wilson (1985) studied just such a rubble-dwelling fauna in the Ordovician of Kentucky.” The authors then discussed “another interpretation” of the paleoecologic succession described in Wilson (1985). Because the Ordovician succession described by Wilson may be one of the few valid examples of an autogenic ecological succession in the fossil record (see Miller, 1986) the re-interpretation by Kobluk and Lysenko (1987) must be answered.

Some factors affecting the respiration of intertidal Asterina gibbosa (Echinodermata: Asteroidea)

In Britain, the cushion star Asterina gibbosa Pennant 1897 (Echinodermata, Asteroidea) is confined to the west coast, where it occurs on rocky shores, often sympatrically with the closely related Asterina phylactica Emson & Crump 1979 (Crump & Emson, 1983; Emson & Crump, 1984). The vertical distribution of A. gibbosa extends from about 100 m depth, into the intertidal; however, littoral cushion stars occupy rock pools and relatively damp habitats such as gulley walls, crevices, overhangs and the underside of boulders, generally on the lower shore (Emson, 1979). On shores with rock pools, cushion stars may extend their upper limits of vertical distribution but not beyond the mean high-water neap-tide level (Crump & Emson, 1978). Absence of A. gibbosa from higher shore levels has been related to intolerance to desiccation and high temperature, inadequate food supply, and complex behavioural responses to gravity and light (Crozier, 1935; Emson, 1979; Crump & Emson, 1983). Prior to the present study, it has not been possible to discuss the influence of respiratory requirements on the vertical distribution of this species.

Disturbance and organisms on boulders

Several aspects of disturbance by waves to intertidal boulders were monitored for one year high and low on the shore on two rock platforms on the east coast of Australia. These boulders were also subjected to burial by sand, and this disturbance was monitored in the same places for two years. The mobile and sessile organisms on the tops and bottoms of the rocks were sampled six times during the same period in order to determine patterns in community structure and assess the role of disturbance. Small rocks were overturned more often and buried to a greater extent than large rocks, but rocks of all sizes were moved similar distances with similar frequency. These contrasting results were probably caused by the fact that small rocks were rounder than large rocks. Rocks were buried in sand much more at Long Reef than at Cape Banks, but differences among places in disturbance by waves were not great.Patterns in community structure were complex but suggested that disturbance was only important for sessile organisms on the undersides of boulders. The number of sessile species present was always related to the size of the rock but the total cover of algae on the tops of rocks never was. Some particular species were most abundant on large rocks but others showed the reverse pattern, covering more space on the smaller boulders. This latter pattern may have been due to the shorter period of exposure during low tide in this situation, though grazers were also abundant on these rocks in some places. In contrast, nearly all species on the undersides of rocks reached greatest abundance on the medium to large rocks, consistent with effects of disturbance. Space was in short supply low on the shore and overgrowth apparently reduced diversity but this was not the case elsewhere. Overall, the results indicate that disturbance was frequent and important, but not for all species nor in all places.

Activity pattern as a mechanism of predator avoidance in two species of acmaeid limpet

Activity patterns in the foraging activity of two species of acmaeid limpets, Collisella limatula (Carpenter, 1864) and C. scabra) (Gould, 1846) were documented over the entire tidal cycle. C. limatula was found to be active only while awash by the tide and during night-time emergence; periods of inactivity were spent in crevices and on the undersides of boulders. C. scabra, which homes to a scar on the upper surfaces of rocks, foraged only while awash in daylight. The activity pattern of C. limatula was demonstrated to be an effective mechanism for avoiding predation by Octopus, a major visual predator of limpets, in both laboratory and field experiments. The homing habit of Collisella scabra was also shown to reduce the rate of predation in the laboratory. It is suggested that the observed activity patterns have evolved in response to predation pressure from swift-moving visual predators.