Coralline Turf Research Articles

Nursery provision of red-algal habitats in temperate Algoa Bay, South Africa

This study examines the importance of both macroalgal heterogeneity and specific macroalgal species or morphotypes to nursery provision for juvenile sparids (Diplodus capensis and Sarpa salpa) in a shallow (< 2 m), sheltered rocky cove in warm-temperate Algoa Bay, South Africa. The rocky cove is comprised of a mosaic of two main benthic habitats; canopy-forming Plocamium corallorhiza beds on rocky outcrops and flat reef dominated by low growing red algae morphotypes. We assessed macroalgal communities and the trophic ecology (stomach contents and isotopes), abundance and size structure of D. capensis and S. salpa in the two different benthic habitats and the resources/food associated with the dominant macroalgae species/morphotypes. We found high densities of S. salpa and D. capensis, in both high profile reef (rocky outcrops) and low profile (flat) reef. Within this habitat mosaic resources (epiphytes and macroinvertebrates) were more abundant in the non-canopy forming low growing macroalgae (Laurencia spp. and coralline turf algae) and these algae were also assimilated in the diets of both sparids. The high abundance of both juvenile S. salpa and D. capensis in high profile and low profile reef, suggests that within this mosaic of habitats these species may be using canopy-forming algae in the high profile reef for shelter and non-canopy forming algae in both the high and low profile reef for food. This shows that macroalgal habitats comprising several morphotypes have the potential to support higher juvenile diversity and abundance through both food provision and shelter.

A case study on the function of turf algae as suitable habitat for peracarid crustaceans in disturbed environments from SW Mediterranean Sea

ABSTRACT In the summer of 2014, a field study was carried out in four coastal rocky bottoms from the southeast coast of Spain. In this region, dense canopies of Ericaria mediterranea characterize the undisturbed areas and cover much of the infralittoral stage. Turfs composed of the coralline algae Ellisolandia elongata replace the canopy in places where any anthropogenic disturbance occurs. The main objective of this study was to compare the peracarid fauna inhabiting within the two types of phytal substrate, and to conduct several statistical analyses to detect significant differences between the two assemblages. Contrary to expected, the analyses showed that in E. elongata there was a higher population density of peracarids, as well as higher species richness and values for α-diversity indexes. However, none of these differences was statistically significant, although site-to-site comparison indicated greater differences between locations with the same physical cover. The data pointed out that the assemblage that inhabits the coralline turfs in the area was not an impoverished version of that found in pristine locations, so these algae can act as a suitable habitat for peracarids in case of mild human disturbance.

Long-term community shifts driven by local extinction of an iconic foundation species following an extreme marine heatwave.

Gradual ocean warming combined with stronger marine heatwaves (MHWs) can reduce abundances of foundation species that control community structures, biodiversity, and ecosystem functioning. However, few studies have documented long-term succession trajectories following the more extreme events that cause localized extinctions of foundation species. Here, we documented long-term successional changes to marine benthic communities in Pile Bay, New Zealand, following the Tasman 2017/18 MHW, which caused localized extinctions of dominant southern bull kelp (Durvillaea sp.). Six years on, multiscale annual and seasonal surveys show no sign of Durvillaea recolonization. Instead, the invasive annual kelp (Undaria pinnatifida), rapidly colonized areas previously dominated by Durvillaea, followed by large changes to the understory community, as Durvillaea holdfasts and encrusting coralline algae were replaced by coralline turf. Between 3 and 6 years after the total loss of Durvillaea, smaller native fucoids colonized in high densities. Although Undaria initially colonized plots throughout Durvillaea's tidal range, later in the succession Undaria only retained dominance in the lower intertidal zone and only in spring. Ultimately, the tidal zone was slowly replaced by alternative foundation species, composed of different canopy-forming brown seaweeds that dominated different intertidal elevations, resulting in a net increase in canopy and understory diversity. This study is a rare example of long-term effects following an extreme MHW that caused extinctions of a locally dominant canopy-former, but these events and their associated dramatic changes to community structures and biodiversity are expected to become increasingly common as MHWs continue to increase in strength, frequency, and duration.

Influence of ocean warming and acidification on habitat-forming coralline algae and their associated molluscan assemblages

When ocean warming and acidification impact habitat-forming species, substantial alterations to the supported ecological communities and associated ecosystems are likely to follow. Here, we used experimental manipulations to test the hypotheses that ocean warming and acidification would negatively affect habitat-forming coralline algal turfs and the diverse molluscan assemblages they support. Boulders covered in a turf of Amphiroa anceps with intact faunal assemblages were subjected to an orthogonal combination of current (~ 23 °C) and future (~ 26 °C) ocean temperatures, and current (~ 430 µatm) and future (~ 880 µatm) seawater pCO 2 . Ocean warming negatively impacted the cover and photosynthetic efficiency of Amphiroa fronds, whereas ocean acidification caused the biomass per unit area and the frond density of Amphiroa turf to be 56% and 59% less than current ocean conditions, respectively. Ocean acidification also caused a significant change in the structure of molluscan assemblages associated with Amphiroa turf, which included a 43% and a 61% reduction in the species richness and overall abundance of molluscs, respectively. The results demonstrate that coralline algal turfs are particularly vulnerable to ocean climate change, which has implications for the biodiversity and ecosystem functions supported by these globally distributed foundation species. • We assessed whether ocean warming and acidification impacts habitat-forming coralline algal turfs and their associated molluscan assemblages. • Ocean warming negatively impacted the cover and photosynthetic efficiency of coralline fronds. • Ocean acidification caused a 56% and a 59% reduction in the biomass and frond density of coralline turfs, respectively. • Ocean acidification caused a decrease in the richness and abundance of molluscs in coralline turfs by 43% and 61%, respectively.

Positive and Negative Species Interactions Shape Recruitment Patterns of a Range Expanding Native Alga

A species’ ability to spread is in part governed by the extent to which recipient habitats either resist, tolerate or promote the species’ recruitment. In disturbed marine environments, there is a general trend for the loss of algal canopies, thought to resist invasion, toward algal turf or rock barrens habitat. This study tested whether the spread of the range-expanding native macroalga Caulerpa filiformis was resisted by algal canopies but facilitated by algal turf or barrens habitats. Large-scale field surveys generally supported the predicted recruitment patterns, with C. filiformis recruits being most abundant on turf (but not barrens) and absent under kelp canopies. However, a discrepancy existed between different structural forms of turf, with the positive association holding true only for geniculate corallines, not filamentous turf. Secondly, a laboratory experiment tested whether the physical structure and/or the sediment-trapping properties of coralline turf influenced the recruitment success of C. filiformis. Whilst the structural complexity of turf aided overall recruitment performance (i.e., increased rhizoid production, attachment speed, success, and strength), a positive influence of turf-derived sediment on recruits’ growth was less obvious, at least over 10 days. The high morphological plasticity of C. filiformis propagules resulted in possible benefits of faster or stronger attachment of more developed propagules being only temporary, and that recruitment may be regulated in accordance with habitat preference. Finally, a field experiment confirmed the observed positive role of turf and the negative influence of algal canopies in the short-term, however, adverse environmental conditions in the longer-term resulted in the loss of most fragments. In conclusion, this study demonstrated the importance of both positive and negative species interactions for the recruitment success of a native alga, suggesting that a shift from kelp to turf algae can initiate further community change.

Demography of the Intertidal Fucoid Hormosira banksii: Importance of Recruitment to Local Abundance.

Canopy-forming macroalgae form the basis of diverse coastal ecosystems globally. The fucoid Hormosira banksii is often the dominant canopy-forming macroalga in the temperate intertidal of southern Australia and New Zealand, where it is commonly associated with an understory of coralline turf. Hormosira banksii is susceptible to both natural and anthropogenic disturbance and despite its abundance, few studies have examined the demography of this important species. This study determined the demographic response of H. banksii to different gradients of disturbance to both its canopy and to the understory coralline turf. We established plots in which the density of H. banksii and/or understory coralline turf was manipulated in a pulse perturbation to simulate a disturbance event. The manipulated plots contained eight treatments ranging from 100% removal of H. banksii to 100% removal of the understory coralline turf. We then measured recruitment and followed individual recruits for up to 18months to determine growth and survivorship. We found that H. banksii recruitment was seasonally variable throughout the experiment and highest over summer, survivorship of recruits was generally high, and the species was slow-growing and long-lived. Moreover, the level of disturbance did not seem to affect recruitment, growth, or survivorship and post-recruitment mortality was independent of H. banksii density. In this system, it appears that H. banksii is a relatively long-lived perennial species whose demography is density-independent which appears to allow recovery from disturbance.

Ecosystem functioning of canopy- and turf- forming algae: contrasting supply of invertebrate prey to pelagic consumers

Macroalgal canopies are declining worldwide and are being replaced by low-lying algal turfs which frequently dominate reefscapes. Their loss may impact reef ecosystems in different ways, including the collapse of small canopy-dwelling invertebrates, and thus the decline of juvenile reef fish that prey on them. To evaluate this potential loss, we assessed (1) the differences between the mobile invertebrate assemblages associated with turf-forming (filamentous and articulated coralline turf) and canopy-forming (Sargassumspp. andDichotomaria marginata) algae, and (2) the mechanisms underlying those contrasts by examining the invertebrate community assembly of filamentous turf andSargassumspp. over the main canopy season. Abundance, biomass and diversity almost always differed between canopies and turfs (although not in a consistent way across sampling sites), while differences within canopy and turf algal types were nearly absent. The structure of invertebrate assemblages differed more consistently between canopies and turfs, with certain hard-bodied and soft-bodied invertebrates characterizing canopies and turfs, respectively. This divergence increased as the canopy season advanced. While no temporal changes occurred in turf invertebrate assemblages, clear temporal dynamics occurred in the invertebrate fauna associated withSargassum.Brittle stars and amphipods were most abundant as early colonizers, followed by hard-shelled gastropods, bivalves and ostracods. By the end of the season, these groups became dominant and decreased diversity in the canopy habitat. As hard-shelled prey are preferred items for the main invertivore fish species in the area, results suggest that canopies may play an important role in the provisioning of trophic resources to pelagic consumers.

Resistance, Extinction, and Everything in Between – The Diverse Responses of Seaweeds to Marine Heatwaves

Anomalously Globally, anomalously warm temperature events have increased by 34% in frequency and 17% in duration from 1925 to 2016 with potentially major impacts on coastal ecosystems. These ‘marine heatwaves’ (MHWs) have been linked to changes in primary productivity, community composition and biogeography of seaweeds, which often control ecosystem function and services. Here we review the literature on seaweed responses to MHWs, including 58 observations related to resistance, bleaching, changes in abundance, species invasions and local to regional extinctions. More records existed for canopy-forming kelps and bladed and filamentous turf-forming seaweeds than for canopy-forming fucoids, geniculate coralline turf and crustose coralline algae. Turf-forming seaweeds, especially invasive seaweeds, generally increased in abundance after a MHW, whereas native canopy-forming kelps and fucoids typically declined in abundance. We also found three four examples of regional extinctions of kelp and one example of fucoids extinction following specific MHWs, events that likely have long term consequences for ecological structure and functioning. Although a relatively small number of studies have described impacts of MHWs on seaweed, the broad range of documented responses highlights the necessity of better baseline information regarding seaweed distributions and performance, and the need to study specific characteristics of MHWs that affect the vulnerability and resilience of seaweeds to these increasingly important climatic perturbations. A major factor will be to disentangle impacts caused by the extreme temperature increases of MHWs itself from co-occurring potential stressors including altered current patterns, changes in water clarity and nutrient content, solar radiation and desiccation stress in the intertidal zone. With future increases anticipated in the intensity, duration and frequencies of MHWs, we expect to see more replacements of large long-lived habitat forming seaweeds with smaller ephemeral weeds, reducing the structure and effective services seaweed-dominated reefs can provide.

Effects of sediment on early life history stages of habitat-dominating fucoid algae

The effects of sediment on settlement and early post-settlement survival of habitat-dominating fucoid algae have not been extensively investigated. Two separate experiments tested whether different size-fractions, abundances and types of sediment differentially affect the attachment of Hormosira banksii and Cystophora torulosa zygotes under laboratory conditions, and whether alteration of the sediment environment differentially affects early post-settlement survival of fucoid zygotes placed into the natural environment. In the laboratory, an average of c. 59% of Hormosira zygotes were able to attach to primary substratum in the presence of sparse sand and silt, compared to 28% (silt) and 39% (sand) of Cystophora zygotes. In the presence of dense sand or silt, <8% of either species attached to primary substratum, with the great majority of zygotes of both species attaching to sediment grains. In the field, Hormosira zygotes across three treatments survived for the entire two week experimental period, whereas no Cystophora zygotes survived beyond 8 days. For both species there was a gradient of survival across treatments, from the poorest survival on bare rock, slightly better survival in coralline turf that contained sediments, and greater survival in coralline turf with the sediment removed, although there were significant interactive effects of treatment and time. After two weeks, an average of 22% of Hormosira zygotes survived on bare rock, around 38% on coralline turf with sediment, and 40% on coralline turf minus sediment, but with high variation in the treatments. On day 5 of the field experiments, when zygotes of both species remained across treatments, there were significant differences between species and between treatments which mirrored results across the whole experiment. Overall, the experiment showed that the sediment environment influenced both the attachment of fucoid zygotes and early post-settlement survival. The experiments highlighted key differences between species in their method of attachment and subsequent interactions within the abiotic environment, with the larger stickier zygotes of Cystophora more readily attaching to sediment grains, and the less sticky Hormosira zygotes often rolling through the sediments and attaching to the primary substratum. These early life history characteristics of key species and their interaction with those of microsites in which they settle clearly have importance to the replenishment and maintenance of populations.

The importance of shore height and host identity for amphipod assemblages

ABSTRACTThe spatial distribution of organisms associated with marine intertidal macroalgae may be a direct result of their tolerance to air exposure or an indirect consequence of the distribution of their host. We compared amphipod assemblages from five intertidal macroalgae to investigate their relationship with algal identity. To test the effect of height regardless of algal characteristics, we transplanted coralline algal turfs to three different levels within the intertidal zone and compared amphipod assemblages after 1 and 14 days. Interstitial volume was positively correlated to the abundance of amphipods, suggesting that this attribute may correspond better to the potential space for their occupation when compared to algal biomass, thallus volume or the ratio between thallus and interstitial volume. Algal level determined the structure of the amphipod assemblages. Upper-level (Acanthophora spicifera and Caulerpa racemosa) and intermediate-level (coralline) algae host similar amphipod assemblages dominated by Apohyale media, but different from lower-level algae (Padina gymnospora and Sargassum cymosum), which were dominated by Hyale niger. Ten of the 15 amphipod species reported from natural communities were found in the transplanted plots. Distinct pools of amphipod species colonized coralline transplants at upper and lower levels after 1 day. However, regardless of the position on the shore, transplanted coralline turfs supported similar assemblages after 14 days, indicating that algal identity is also important for species assemblages. Our results suggest that both height on the shore and host identity combine to determine the vertical structure of amphipod assemblages in the rocky intertidal.

Benthic Crustacea from tropical and temperate reef locations: differences in assemblages and their relationship with habitat structure

Tropical and temperate marine habitats have long been recognised as fundamentally different system, yet comparative studies are rare, particularly for small organisms such as Crustacea. This study investigates the ecological attributes (abundance, biomass and estimated productivity) of benthic Crustacea in selected microhabitats from a tropical and a temperate location, revealing marked differences in the crustacean assemblages. In general, microhabitats from the tropical location (dead coral, the epilithic algal matrix [algal turfs] and sand) supported high abundances of small individuals (mean length = 0.53 mm vs. 0.96 mm in temperate microhabitats), while temperate microhabitats (the brown seaweed Carpophyllum sp., coralline turf and sand) had substantially greater biomasses of crustaceans and higher estimated productivity rates. In both locations, the most important microhabitats for crustaceans (per unit area) were complex structures: tropical dead coral and temperate Carpophyllum sp. It appears that the differences between microhabitats are largely driven by the size and relative abundance of key crustacean groups. Temperate microhabitats have a higher proportion of relatively large Peracarida (Amphipoda and Isopoda), whereas tropical microhabitats are dominated by small detrital- and microalgal-feeding crustaceans (harpacticoid copepods and ostracods). These differences highlight the vulnerability of tropical and temperate systems to the loss of complex benthic structures and their associated crustacean assemblages.

Ecological tipping points for an invasive kelp in rocky reef algal communities

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 587:93-104 (2018) - DOI: https://doi.org/10.3354/meps12429 Ecological tipping points for an invasive kelp in rocky reef algal communities David R. Schiel1,*, Stacie A. Lilley1, Paul M. South2 1Marine Ecology Research Group, School of Biological Sciences, University of Canterbury, Christchurch, New Zealand 2Cawthron Institute, Nelson, New Zealand *Corresponding author: david.schiel@canterbury.ac.nz ABSTRACT: Invasive species are affecting coastal ecosystems worldwide and there are many potential mechanisms that allow their spread into native communities. To investigate this phenomenon, we used an experiment in which the canopy of the southern bull kelp Durvillaea antarctica was removed in 2 seasons and community development was followed over 3 yr. The invasive kelp Undaria pinnatifida recruited almost exclusively into plots from which the natural canopy had been removed. We examined, through a series of regression tree models and change point analyses, the gradients of community responses that allowed the successful recruitment of this invasive species. Analyses revealed a range of coinciding conditions, especially a decline in fucoid cover below 20% and an increase in turf cover above 80%, that facilitated Undaria recruitment. The abundance of molluscan grazers and cover of subcanopy algae had lesser effects on Undaria recruitment. In an ecological sense, there was a clear tipping point in the interaction between canopy loss and the subsequent expansion of coralline turf that allowed communities to switch from dominance by native species to seasonal dominance of Undaria. This study illustrates the complex nature of disturbance thresholds and interactions within the native communities that can facilitate the spread and recruitment success of Undaria. KEY WORDS: Tipping point · Threshold · Rocky reef · Native algae · Invasive algae · Regression tree Full text in pdf format PreviousNextCite this article as: Schiel DR, Lilley SA, South PM (2018) Ecological tipping points for an invasive kelp in rocky reef algal communities. Mar Ecol Prog Ser 587:93-104. https://doi.org/10.3354/meps12429 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 587. Online publication date: January 25, 2018 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2018 Inter-Research.

Non-trophic responses of algal communities to nutrient enrichment: interactions among coralline turfs, ephemeral algae and perennial fucoids

Non-trophic responses of algal communities to nutrient enrichment: interactions among coralline turfs, ephemeral algae and perennial fucoids

Biological traits and taxonomic composition of invertebrate assemblages associated with coralline turf along an environmental gradient

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 530:15-27 (2015) - DOI: https://doi.org/10.3354/meps11337 Biological traits and taxonomic composition of invertebrate assemblages associated with coralline turf along an environmental gradient Anna K. Berthelsen1,*, Judi E. Hewitt2, Richard B. Taylor1 1Leigh Marine Laboratory, University of Auckland, PO Box 349, Warkworth 0941, New Zealand 2National Institute of Water and Atmospheric Research, PO Box 11-115, Hamilton 3216, New Zealand *Corresponding author: annakateberthelsen@gmail.com ABSTRACT: Biological traits relating to the behaviour, morphology and life history of organisms can influence ecological functioning, and this principle is becoming increasingly used to examine the functional response of communities to environmental variation. We quantified the taxonomic and biological traits composition, and the overall abundance and richness, of small (1-8 mm) mobile invertebrate assemblages inhabiting subtidal coralline algal turf (Corallina officinalis) along an environmental gradient ranging from (1) relatively deep, wave-exposed sites with short turf containing a low proportion of fine sediment to (2) shallow wave-sheltered sites with taller turf containing a higher proportion of fine sediment. Turf fauna were diverse (118 taxa) and abundant (12000-53000 ind. m-2), with assemblages dominated by amphipods and gastropods. Total abundances of invertebrates were higher at the wave-exposed sites. When analysed in multivariate space using proportional abundance, replicates based on taxonomic composition grouped more strongly by site along the overall gradient than those based on traits. As proportions of biological traits remained relatively stable along the gradient, numbers of all traits possessed by individuals were higher at the wave-exposed end of the gradient. Although some environmental variables contributed significantly to explaining multivariate trait and taxa patterns, most individual correlations between environmental variables and traits and taxa were weak. This study shows that biological traits can be shared between taxonomically distinct assemblages of turf-dwelling invertebrates, and indicates a relatively small influence overall of environmental variables on the composition of traits and taxa. KEY WORDS: Temperate rocky reef · Diversity · Algal morphology Full text in pdf format Supplementary material PreviousNextCite this article as: Berthelsen AK, Hewitt JE, Taylor RB (2015) Biological traits and taxonomic composition of invertebrate assemblages associated with coralline turf along an environmental gradient. Mar Ecol Prog Ser 530:15-27. https://doi.org/10.3354/meps11337 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 530. Online publication date: June 18, 2015 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2015 Inter-Research.

Coralline turf-associated fauna are affected more by spatial variability than by host species identity

We examined the effects of host species identity and spatial variability on animals inhabiting subtidal coralline algal turfs, by comparing the assemblages of small (1–8 mm) mobile invertebrates associated with five coralline turf species across a number of subtidal rocky reefs in northeastern New Zealand. Coralline turf fauna were abundant (average of 16,000 to 80,000 ind.m−2) and diverse (129 taxa in total), with assemblages dominated by arthropods, gastropods and polychaetes. Despite substantial differences in the morphologies of the coralline turf species, host identity had little effect on total abundance and richness of the fauna, and a moderate effect on taxonomic composition. Spatial variation at the scale of 102–103 m had a stronger influence than host identity on all three assemblage-level properties, with wave exposure and depth having the most explanatory power of the environmental factors measured. Host-specificity was low, probably due to the close taxonomic relatedness of the host algal species and their inedibility (with consequent lack of dietary specialisation by fauna). For our study system, the results justify the common practice of lumping coralline turf species in ecological studies with regard to the description of the total abundance and richness of the associated fauna, but not the taxonomic composition of the fauna.

Effects of algal turfs and sediment accumulation on replenishment and primary productivity of fucoid assemblages

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 511:59-70 (2014) - DOI: https://doi.org/10.3354/meps10932 Effects of algal turfs and sediment accumulation on replenishment and primary productivity of fucoid assemblages T. Alestra1,*, L. W. Tait2, D. R. Schiel1 1Marine Ecology Research Group, School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch 8041, New Zealand 2National Institute of Water and Atmospheric Research (NIWA), 10 Kyle Street, PO Box 8062, Riccarton, Christchurch 8011, New Zealand *‑Corresponding author: tommaso.alestra@pg.canterbury.ac.nz ABSTRACT: As a result of anthropogenic habitat degradation worldwide, coastal ecosystems are increasingly dominated by low-lying, turf-forming species, which proliferate at the expense of complex biogenic habitats such as kelp and fucoid canopies. This results in dramatic alterations to the structure of the associated communities and large reductions in primary productivity. The persistence of turf-dominated systems has been attributed to the impacts of the turfs on the recovery of algal canopies and also to the different susceptibility of canopy- and turf-forming algae to altered physical conditions, in particular increased sedimentation. Here we tested the impacts of turfing geniculate coralline algae and sediment on fucoid recovery dynamics and their influence on assemblage net primary productivity (NPP). The recruitment of the habitat-forming fucoid Hormosira banksii on bare substrata was significantly higher than in treatments in which sediments, coralline turfs or turf mimics covered the substratum, indicating that sediment deposition and space pre-emption by algal turfs can synergistically affect the development of fucoid beds. NPP of coralline turfs was much lower than that of fucoid-coralline assemblages, which included a H. banksii canopy, and was reduced further by sediment accumulation. When devoid of sediment, however, coralline algae contributed to enhance fucoid-coralline assemblage NPP, because of synergistic interactions among the components of the multi-layered assemblage in optimizing light use. Our findings amplify extensive research addressing the global loss of macroalgal canopies and highlight key processes involving sediment accumulation in the benthic environment and effects on the replenishment and productivity of fucoid stands. KEY WORDS: Canopy · Coralline algae · Habitat structure · Intertidal · Macroalgae · Photosynthesis · Sediment · Turf-forming Full text in pdf format PreviousNextCite this article as: Alestra T, Tait LW, Schiel DR (2014) Effects of algal turfs and sediment accumulation on replenishment and primary productivity of fucoid assemblages. Mar Ecol Prog Ser 511:59-70. https://doi.org/10.3354/meps10932 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 511. Online publication date: September 24, 2014 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2014 Inter-Research.

Impacts of natural and manipulated variations in temperature, pH and light on photosynthetic parameters of coralline–kelp assemblages

Increasing absorption of CO2 by the world's oceans is lowering seawater pH and may have severe consequences for marine calcifying organisms. Understanding the ecological consequences of anthropogenic CO2 emissions will require examination of how calcifying organisms and their associated communities respond to natural variation in CO2 concentration. Many macroalgae may respond positively or neutrally to ocean acidification, but calcifying species such as coralline algae are predicted to be some of the most susceptible organisms to changing CO2. Here I test the impacts of temperature and pH variation on important photosynthetic metrics of macroalgal assemblages composed of coralline turf, Corallina vancouveriensis and the associated canopy-forming kelp, Saccharina sessilis using in situ photorespirometry and laboratory mesocosms. In situ photorespirometry was done at two locations on the Oregon (USA) coast, an area with variable upwelling of high CO2, low pH water. To complement in situ measurements, a series of laboratory mesocosms were used to disentangle the effects of pH and temperature on photosynthetic parameters across a light gradient. The acute effects of low pH were also tested across a temperature gradient, revealing an exacerbated effect of short duration, low pH events on respiration rates at increasing temperature. NPP (net primary productivity) was reduced by 10–20% within in situ coralline assemblages across a natural gradient of pH (8.1–7.9), but there was a mostly neutral effect of low pH on NPP of coralline–kelp assemblages. These results indicate varied responses of coralline and coralline–kelp assemblages to temperature and pH gradients, but under limiting light conditions primary production and growth of corallines are likely to decrease under modest scenarios of CO2 increase. Assemblage composition could play an important role in modulating the impacts of ocean acidification on calcifying organisms, and results from this study suggest that canopy and sub-canopy interactions could determine the response of susceptible species to changing climatic parameters.

Restoration of the habitat-forming fucoid alga Hormosira banksii at effluent-affected sites: competitive exclusion by coralline turfs

Fucoid algae often dominate intertidal rocky shores, providing habitat and modifying ecosystem resources for other species, but are susceptible to discharge of sewage effluent. In this study we assessed the potential for competition from coralline turfs to inhibit restoration of the inter- tidal fucoid macroalga Hormosira banksii at sites associated with an ocean outfall a scenario of improving following water quality in the nearshore coastal environment. The percentage cover and number of individuals of H. banksii were negatively correlated with both the percentage cover and turf height of Corallina officinalis. In contrast, H. banksii was positively associated with rocky sub- strata and recruited well to rock-surface substrata. Importantly, there appears to be a threshold abun- dance where the percentage cover of H. banksii rarely reaches above 20% cover amongst coralline turfs with >40% cover. These data support a model of alternative community states: H. banksii dominated canopy on rocky substrata versus C. officinalis turf. In field and laboratory experiments, extensive coralline turfs (up to 4 cm thick) were shown to inhibit recruitment of H. banksii. This study shows competitive exclusion by coralline turfs may limit the successful restoration of habitat provided by H. banksii to shores that have been affected by sustained discharge of secondarily treated sewage effluent. We suggest potential strategies for management authorities to consider when seeking ways of restoring fucoid communities affected by anthropogenic disturbances such as wastewater disposal.

Limited Recovery of the KelpEisenia bicyclisAfter Population Reduction of the Sea UrchinsHemicentrotus pulcherrimusandAnthocidaris crassispinaon Kii Peninsula, Southwestern Japan

We gauged the effect of the sea urchins Hemicentrotus pulcherrimus and Anthocidaris crassispina on an Eisenia bicyclis kelp bed on the Kii Peninsula in southwestern Japan. We monitored sea urchin density, size, and vertical algal distribution every 2 months from September 2000 to March 2002 and in September 2002 in a 40-m2 plot that stretched from the intertidal (reef) zone to the subtidal zone at depth of up to 2 m. The sea urchin densities were more than 40 individuals/m2 (H. pulcherrimus) and more than 5 individuals/m2 (A. crassispina) during September 2000 to May 2001. These densities decreased abruptly to less than 20 and less than 1 individual/m2 in October 2001, respectively, coincident with low salinities of less than 23 practical salinity unit (PSU) in late June because of river water inflow. Until May 2001, adult E. bicyclis grew only on the intertidal reef, and articulated coralline turf was predominant in the subtidal zone. From January 2002, the kelp bed expanded slightly to the upper subtidal zone, but most young kelp growing at a depth of more than 1.5 m disappeared, despite the low sea urchin density. It is likely that abiotic factors resulting from the river water inflow inhibited the growth of E. bicyclis.

Densities of polychaetes in habitat fragments depend on the surrounding matrix but not the complexity of the remaining fragment

AbstractBiogenically engineered habitats are constantly changing in space and time, resulting in changes to the landscape and the ecology of associated taxa. Using patchily distributed biogenic habitats on intertidal rocky shores the influences of different aspects of the landscape were investigated, that is, the surrounding matrix and the habitat itself. Experiments to test the effect of the matrix were carried out by transplanting assemblages in artificial habitats from one type of biogenically engineered matrix (created by the tubeworm Galeolaria caespitosa) to another (created by the oyster Saccostrea glomerata). Change to the surrounding matrix resulted in the densities of polychaete worms in central fragments of habitat changing to become more similar to their new surroundings. To test how the habitat influenced predator–prey interactions, polychaetes were transplanted from a complex habitat (created by the turfing alga Corallina officinalis) to less complex habitat (created by the tubeworm G. caespitosa), with or without the presence of the predatory polychaete, Perinereis amblyodonta. This experiment also tested the influence of habitat replacement on densities of polychaetes, regardless of any new interactions between species. Despite coralline turf being a much more complex habitat than Galeolaria, P. amblyodonta successfully preyed on other species of polychaetes in both habitats. Furthermore, in the absence of P. amblyodonta, survival of polychaetes did not differ between the habitats. These types of experiments will be useful for testing similar hypotheses in different landscapes and will assist in gaining a more general understanding of habitat modification.