Artificial Kelp Research Articles

Combining ecology and technology to kick‐start oyster reef restoration

Techniques that enhance the recruitment of foundation species to restoration sites can inform the ecological development of the restored habitat. However, techniques are often considered in isolation, potentially overlooking synergies from combining them. Native oyster reefs have been lost worldwide, resulting in restoration efforts in systems that are often recruitment limited, or where recruiting oysters must spatially compete with opportunistic species. Here, we present a field‐based study that combines ecological knowledge on positive species interactions with novel acoustic technology, both of which are demonstrated to boost oyster recruitment in isolation, to test whether their interaction synergistically enhances the early larval recruitment that drives oyster reef development. At three sites across a 20 ha oyster reef restoration in southern Australia, we used self‐made speakers to broadcast healthy reef soundscapes that attract oysters and combine this with artificial kelp that facilitates oyster recruitment by suppressing competitive species (turfing algae). The combination of acoustic enrichment and artificial kelp increased oyster recruitment to the topside of substrate (326.98% increase), whereas only acoustic enrichment increased recruitment to the underside of substrate (126.95% increase). Our findings suggest that the combination of multiple techniques and their interactive effects might boost the early stages of reef development, providing proof‐of‐concept that these approaches can help oysters to build and bind reefs (i.e. recruit to the topside and underside, respectively). By combining ecology with technology during the first stages of a developing reef restoration, we show the potential value of these novel approaches to kick‐start the recovery of lost oyster reefs.

Trophic Assessment of an Artificial Kelp Eisenia bicyclis Bed Off the Eastern Coast of Korea Based on Stable Isotope Analyses

Effective trophic assessment of restoration success after the creation of an artificial habitat is essential for ecological management. In this study, to evaluate the ecological trophic function of restored kelp beds of artificial macroalgal reefs (AMRs) attached with the kelp species Eisenia bicyclis, we compared carbon and nitrogen stable isotope ratios of organic matter sources and macrobenthic consumers and isotopic indices of functional feeding groups between artificial and reference (natural bed and barren ground, respectively) habitats. There were no significant differences in isotopic values of consumer feeding groups (except for carnivores) and their potential food sources between the artificial and natural sites, suggesting that resource diversity and resource use by consumers was similar across all sites. The isotopic data also exhibited similar or relatively higher trophic niches of feeding groups at the artificial site compared to those at the natural site, indicating that the artificial kelp bed can play important roles in similar ecological functions and services as a natural counterpart. In addition, the present study revealed that the isotopic ranges and niche indices of feeding groups were significantly wider at the artificial and natural kelp beds compared to those at the barren ground, suggesting the trophic importance of macroalgal-derived organic matter to consumer nutrition in coastal ecosystems. Overall, our results support the conclusion that the creation of an Eisenia bicyclis kelp bed by the AMRs may lead to the restoration success of the macroalgae habitat through the recovery of the ecological function of a natural food web structure.

Investigating public preferences for the management of native and invasive species in the context of kelp restoration

The Southern Rock Lobster (Jasus edwardsii) is key to management of the Long Spined Sea Urchin (Centrotephanus rodgersii). The southern shift of the urchin has created ‘urchin barrens’ of the kelp forests (Ecklonia radiata and Macrocystis pyrifera) in coastal waters off the East Coast of Tasmania. Consistently high fishing efforts of large Southern Rock Lobster in the region has reduced natural predation of the urchin. A number of restoration options exist but these options have not been tested for acceptability with the public to date. In this study we estimate the willingness to pay by households in Tasmania for Southern Rock Lobster habitat and management. The willingness to pay estimates can be used in benefit-cost analysis of the various combinations of restoration options supporting decision-making in this Australian marine planning context. Results indicate that direct replanting of kelp is worth $37 per household per year for five years and a 1% increase in the area of marine reserves is worth $2 per household per year for five years. Direct intervention to control sea urchin populations by reintroducing Rock Lobsters or capturing and crushing urchins is worth $33 and $31 respectively per household per year for five years. Households did not support artificial kelp beds installations or subsidising urchin farming operations.

Oxygen metabolism shapes microbial settlement on photosynthetic kelp blades compared to artificial kelp substrates.

We examined factors shaping community assembly of the bull kelp (Nereocystis luetkeana) microbiome by comparing microbial biofilm formation on photosynthetic kelp blade tissues and artificial kelp substrates ('agar substrates') deployed into a kelp forest. New kelp blade tissues were colonized by markedly distinct microbial taxa relative to agar substrates during the same time interval, even when agar substrates were infused with N. luetkeana blades, suggesting that microbial settlement onto kelp surfaces is more than just attraction to a polysaccharide-rich surface. Further, common seawater taxa such as Colwellia sp. and Psychromonas sp. became abundant on agar substrates but avoided new kelp blade tissues, indicating that host-specific factors may deter certain surface-associated marine microbial taxa. Over two-thirds of the bacterial taxa in the kelp microbiome were associated with strictly aerobic metabolisms; thus, photosynthetic production of O2 may favour aerobic microbial metabolisms. While living kelp blades primarily recruited aerobic microbes, including the obligate aerobe Granulosicoccus sp., microbes that colonized agar substrates were predominantly facultative anaerobes. We also found that infusion of kelp tissues into agar substrates altered microbial community composition and lowered taxonomic diversity relative to control agar substrates, suggesting that non-living components of the kelp blade also impact microbial community assembly.

Development of a water-stable agar-based diet for the supplementary feeding of cleaner fish ballan wrasse (Labrus bergylta) deployed within commercial Atlantic salmon (Salmon salar) net-pens

Abstract The aim of this project was to develop a water-stable and palatable diet for the supplementary feeding of wrasse deployed in salmon sea-pens using a gelling agent mixed with a manufactured dry-feed component. Three binders (gelatine from cold water fish skin, beef gelatin and agar-agar) were compared for water-gel strength over a range of concentrations. Gel formed using agar was found to be significantly stronger than the other binders tested. An experimental aqua-feed made using a grinded, dry ingredient mix binded with 20 g/L agar solution at 1/1.6 (w/v) ratio and offered as blocks within individual feeders was water-stable for 7 days when deployed fresh or following a week of preservation at -20 °C. Farmed ballan wrasse in tanks fed on the agar-based diet within 2 days of deployment. Wild wrasse stocked in salmon sea-pens at low density (1.2–2.1%), up to 4 weeks prior the start of the trial and not previously fed a manufactured diet first ingested the agar feed within 2 weeks and total feed intake significantly increased afterwards. Feed intake was significantly higher from feeders placed within a small feeding shelter made of artificial kelp than within the large wrasse shelter. No nutrient leaching after water immersion and no alterations in the fatty acid profile after preparation of the experimental feed was found. A manufactured grinded ingredient mix binded with 20 g/L agar solution at a 1/1.6 (w/v) ratio and offered within static feeders is proposed as the basis of a novel supplementary feeding methodology for cleaner fish wrasse deployed in salmon sea-pens. This methodology has the potential to facilitate wrasse feeding and to allow the monitoring of feed intake to safeguard the health, welfare and delousing activity of the biological stock over the salmon rearing cycle.

Settlement and early survival of southern rock lobster, Jasus edwardsii, under climate-driven decline of kelp habitats

Abstract Kelp habitats provide food, refuge, and enhance the recruitment of commercially important marine invertebrates. The southern rock lobster, Jasus edwardsii, supports valuable fisheries in southern Australia and New Zealand. Kelp habitats once covered large areas of inshore reef around Tasmania, Australia, but coverage has reduced over the last few decades due to climate change, especially off the eastern coast of the island. We investigated whether the kelp influences the settlement of lobster post-larvae to artificial collectors and how the presence of kelp affected the overnight predation on the early benthic phase (EBP). Settlement of lobster was tracked over 6 months using crevice collectors that had either natural or artificial giant kelp, Macrocystis pyrifera attached, or nothing attached (control). Collectors with natural kelp had higher catches than those with artificial kelp or controls (p = 0.003), which suggested enhanced settlement through chemical attraction. Additionally, we measured overnight predation of the EBP in barren and kelp habitats individually tethered to artificial shelters. The kelp habitat was dominated by brown macroalgal species of Ecklonia radiata, Phyllospora comosa, and M. pyrifera, while the barren was devoid of macroalgae. Survival of the EBP was higher (∼40%) in the kelp habitat than in the barren habitat (∼10%) due to differences in predation (p = 0.016). These results suggest that the kelp habitat improves the recruitment of J. edwardsii and that decline in this habitat may affect local lobster productivity along the east coast of Tasmania.

Three-dimensional resource partitioning between American lobster ( Homarus americanus) and rock crab ( Cancer irroratus) in a subtidal kelp forest

The American lobster ( Homarus americanus) and the rock crab ( Cancer irroratus) commonly coexist, and at high densities, compete for space in subtidal kelp forests in the Gulf of Maine. Competition between the two species was examined in field surveys using visual SCUBA quadrats and complementary laboratory experiments with both live and artificial kelp. Field surveys showed significantly higher crab densities (0.50/m 2 ± 0.08 SE) found up the kelp versus on the ground (0.22/m 2 ± 0.04 SE) when lobsters were present ( P = 0.002). In contrast, crab densities were significantly higher on the ground (0.44/m 2 ± 0.07 SE) as opposed to up the kelp (0.23/m 2 ± 0.06 SE) when lobsters were absent ( P = 0.023). However, the interaction between survey location ⁎ date was significant in five of the eight surveys, suggesting this pattern may not be ubiquitous in all subtidal kelp locations within our study region. Average size of crabs up the kelp or on the ground was not different when lobsters were present or absent ( P > 0.05), and no size correlation was found between lobsters and crabs, irrespective of crab position. Experimental trials in the laboratory confirmed field surveys regardless of the order crabs and lobsters were added into the tank, or the use of live versus artificial kelp, and significant differences were observed in five of the six 5-day experimental trials. Our results suggest that when shelter availability may be limited, kelp could serve as an alternative habitat for rock crabs, perhaps to minimize competition between the two most abundant decapods in the shallow subtidal zone of New England.

ROBUSTNESS OF SURROGATES OF BIODIVERSITY IN MARINE BENTHIC COMMUNITIES

The usefulness of surrogates to estimate complex variables describing community structure, such as the various components of biodiversity, is long established. Most attention has been given to surrogates of species richness and species diversity and has focused on identifying a subset of taxa as a surrogate of total community richness or diversity. In adopting a surrogate measure, it is assumed that the relationship between the surrogate(s) and total richness or diversity is consistent in both space and time. These assumptions are rarely examined explicitly. We examined the robustness of potential surrogates of familial richness and multivariate community structure for macrofauna communities inhabiting artificial kelp holdfasts by comparing among communities of dissimilar ages and among communities established at different times of the year. This is important because most benthic "landscapes" will be a mosaic of patches reflecting different intensities, frequencies, and timing of disturbances. The total abundance of organisms and familial richness of crustaceans or polychaetes were all good predictors of total familial richness (R2 > 0.68). In contrast, while the familial richness of other groups, such as mollusks and echinoderms, were well correlated with total familial richness for communities at an early stage of development, the strength of these relationships declined with community age. For multivariate community structure, carefully selected subsets of approximately 10% of the total taxa yielded similar patterns to the total suite of taxa, irrespective of the age of the community. Thus, useful surrogates of both familial richness and multivariate community structure can be identified for this type of community. However, the choice of technique for selecting surrogate taxa largely depends on the nature of the pilot data available, and careful selection is required to ensure that surrogates perform consistently across different-aged communities. While the specific taxa selected as surrogates will vary among different communities, and possibly even among similar communities at different sites, the techniques and the concepts we address are applicable to any community type.

Effects of habitat complexity on the diversity and abundance of macrofauna colonising artificial kelp holdfasts

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 325:93-100 (2006) - doi:10.3354/meps325093 Effects of habitat complexity on the diversity and abundance of macrofauna colonising artificial kelp holdfasts Alison Hauser, Martin J. Attrill, Peter A. Cotton* Marine Biology and Ecology Research Centre, School of Biological Science, University of Plymouth, Plymouth PL4 8AA, UK *Corresponding author. Email: pete.cotton@plymouth.ac.uk ABSTRACT: Habitat complexity plays an important role in the structuring of ecological assemblages in many terrestrial, freshwater and marine habitats. In this study, we investigated the effects of increased habitat complexity on the diversity and abundance of macrofauna colonising artificial kelp holdfasts of 3 varying levels of complexity. The artificial holdfasts were placed within a kelp bed off the coast of Plymouth for 20 d during the summer of 2004. High complexity holdfast mimics were colonised by significantly higher numbers of individuals and species, and had higher species diversity (Shannon-Wiener H’e), than either the medium or low complexity holdfasts. The relationship between habitat complexity and species diversity has often been attributed to a surface area effect, as habitats with a greater complexity generally also have a greater surface area to support a larger number of species. Therefore, we compared the observed community metrics with the values expected if indices were increasing in proportion to the surface area. We found that the number of species and individuals colonising both the medium and high complexity artificial kelp holdfasts were significantly greater than can be explained by a simple surface area relationship. Species diversity increased less rapidly than expected from the surface area relationship, largely because of a dominance effect from a few abundant species of amphipods and gastropods in the high complexity holdfasts. This study demonstrates that the relationship between habitat complexity and species diversity cannot be explained by surface area alone. KEY WORDS: Habitat complexity · Artificial habitats · Kelp holdfasts · Macrofauna · Colonisation Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 325. Online publication date: November 07, 2006 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2006 Inter-Research.

Determination of Periodate by Fluorescence Quenching of Tetraiodofluorescein

The fluorometric determination of periodate with tetraiodofluorescein has been developed. Under the optimum conditions responses were linear between 4.0×10−7 ∼ 1.0 × 10−5 mol/L of periodate. The detection limit was 1.0 × 10−7 mol/L corresponding to a signal to noise ratio of 2. The proposed method was applied to the determination of periodate in artificial fresh water and kelp sample with good results.

Effect of the kelp Laminaria hyperborea upon sand dune erosion and water particle velocities

This paper presents a set of results from a laboratory study on water wave propagation above submerged vegetation growing in the surf zone and the effect of submerged vegetation on dune erosion. The study has focused on the kelp Laminaria hyperborea. The reason is that this kelp is commercially harvested along the Norwegian coast and there is a need to obtain better knowledge on the possible consequences of this harvesting. Experiments were run with irregular waves over a sloping bottom, and a kelp field was simulated by 5000 artificial kelp plants in a 1:10 scale. The experiments primarily focused on the effect of kelp upon erosion of a sand dune, wave damping and water velocities. It was found that the water level is a very important factor to the degree of dune erosion, while the kelp has only a minor effect. The kelp does, however, cause significant wave damping and the degree of wave breaking is reduced. It was also found that the kelp modifies the water velocity profile. In a region above the kelp canopy layer, the time-averaged water velocity was shoreward, while the seaward undertow was confined to a region higher up in the water column.

Effects of location, exposure and physical structure on juvenile recruitment of the sea urchinStrongylocentrotus droebachiensisin the Gulf of Maine

Summary Studies of juvenile recruitment of the green sea urchin Strongylocentrotus droebachiensis in the Gulf of Maine were conducted during the summer of 1995. These experiments confirmed 12 years of previous observations that settlement only occurs during the months of June and July. Settlement panels were placed at a series of sites along the Maine and New Hampshire coastline to compare recruitment in the northeastern and southwestern regions of the Gulf of Maine. The densities of urchins recruiting in Casco Bay and at the Isles of Shoals were two orders of magnitude higher than those from Eastport and Winter Harbor. There was a discontinuity in settlement densities at Penobscot Bay. Experiments conducted at the Isles of Shoals showed a positive relationship between water motion and larval supply, but neither parameter correlated with recruitment density over eight stations. Contrary to previous results, recuitment was greater within natural, as well as, artificial kelp beds compared to urchin barren a...

Habitat use by juvenile Atlantic cod (Gadus morhua) in the presence of an actively foraging and non-foraging predator

Experiments were conducted in the autumn and winter of 1992/93 to examine habitat use by juvenile (age 0+) Atlantic cod, Gadus morhua L., before, during and following exposure to a passive or actively foraging predator (age 3+ cod). Experiments presented groups of juvenile cod (n=5 fish/group) with one of two combinations of three substrates; (1) gravel, sand, and a patch of artificial kelp (“kelp”), or (2) cobble, sand, and kelp. Cobble is known to provide juvenile cod with a refuge from predation. Kelp was used to test the hypothesis that juvenile cod associate with fleshy macroalgae in nature because of the safety it provides from predators. There was little difference in habitat use by juvenile cod before, during or following exposure to a passive predator. Under these conditions, juvenile cod appeared to prefer finer grained mineral substrates and avoided the kelp. The extent of the juvenile response to a passive predator was to avoid the predator's location in the experimental tank. In contrast, juvenile cod showed a significant shift in habitat use when exposed to an actively foraging predator, hiding in cobble or, when cobble was not available, in kelp. Use of both these habitats resulted in a significant reduction in predation risk to the juvenile cod. Our results suggest that: (1) an association with kelp provides safety from predation to juvenile cod, and (2) juvenile cod are capable for assessing the risk a predator represents and adjust their response accordingly.

The role of kelp detritus in the growth of benthic suspension feeders in an understory kelp forest

Stands of understory kelps greatly alter the physical and biological environment within the algal canopy. In some regions, kelps can also contribute significantly to suspension feeder nutrition through detrital pathways. In a field experiment utilizing artificial kelps, we attempted to decouple and evaluate the physical versus nutritional mechanisms by which understory kelps affect the growth rates of benthic suspension feeders. Suspension feeding organisms were translocated to patches of real and artificial kelps at two subtidal sites, and growth rates measured. Physical parameters were not significantly different between treatments (real versus artificial kelp) and thus any differences in growth rate should be attributable to differences in detrital contribution between real and plastic plants. Of six taxa of suspension feeders examined, only one showed a significant treatment effect and that species grew faster in the artificial kelp treatment. The difference between our result and those of previously published studies may relate to issues of scale and species-specific plant secondary substances.

Kelp beds as habitat for American lobster Homarus americanus

The American lobster Homarus americanus and kelp Laminaria longicruris and L. saccharina are prominent and often intimately associated members of the subtidal community in the western North Atlantic Ocean. However, no one has identified the nature of this relationship or specifically investigated whether kelp beds are a superior habitat for lobsters. We conducted field studies in 1990 and 1991 at a coastal site centrally located along the Gulf of Maine. USA, to determine how lobsters use kelp beds as habitat. Identically sized and spaced plots of live and artificial (plastic) kelp were established and monitored for lobster population densities. Adjacent featureless sediment plots of identical size served as controls. Lobster population density and biomass were significantly higher in both real and artificial kelp treatments than in non-kelp control plots (p < 0 0001). The change in lobster density was apparent the day following placement of the expenment, so a secondary trophic effect such as attracting prey into treatments is unlikely to have occurred. Thus, kelp beds can affect local lobster population dens~ties by providing shelter for lobsters, thereby concentrating individuals and increasing the local carrying capacity of potential lobster habitats The effect of kelp beds on the local carrying capacity of lobster habitats was further explored by test~ng how lobsters respond to differing patch sizes. A graded size series of circular patches of artificial kelp was established, in which kelp blade density and total area were held constant for each treatment. Treatments were subdivided into four 1 m', two 2 m*, or one 4 m2 patches. Experiments were surveyed for lobster population density and size structure to determine if statistical differences existed among treatments. Lobster density was significantly greater in the smallest patches (p c 0.001). Moreover, lobsters typically occupied the edges of kelp beds, and their abundance within kelp patches corresponded to the patch's perimeter-to-area relationship. This suggests that 'edge effects' influence the local carrying capacity for lobsters by influencing the lobsters' choice of kelp beds as habitat.

Wave Attenuation by Vegetation

The vertically two‐dimensional problem of small‐amplitude waves propagating over submerged vegetation is formulated using the continuity and linearized momentum equations for the regions above and within the vegetation. The effects of the vegetation on the flow field are assumed to be expressible in terms of the drag force acting on the vegetation. An analytical solution is obtained for the monochromatic wave whose height decays exponentially. The expressions for the wave number and the exponential decay coefficient derived for arbitrary damping are shown to reduce to those based on linear wave theory and the conservation equation of energy if the damping is small. The analytical solution is compared with 60 test runs conducted using deeply submerged artificial kelp. The calibrated drag coefficients for these runs are found to vary in a wide range and appear to be affected by the kelp motion and viscous effects that are neglected in the analysis. The analytical solution is also shown to be applicable to subaerial vegetation, which is predicted to be much more effective in dissipating wave energy.

Artificial Reefs in the Low Productive Marine Environments of the Southeastern Mediterranean

Abstract. Fishery yields in the oligotrophic waters of the Southeastern Mediterranean arc low due to habitat and food limitations. A four year study of a complex of artificial structures established in the coastal waters of Israel points to several possible solutions to these problems. One approach is the artificial enrichment of the man‐made reef with trash fish. This, together with the configuration of the reef, caused a significant increase in the abundance of fish predators such as groupers of the genus Epinephclus. Omnivores and herbivores were attracted only by the presence of artificial structures. Some species, such as the slipper lobster Scyllurides lulus, only use the man‐made reef for shelter during part of the day or season; they forage over a much larger area the rest of the time and are important “importers” of food to the artificial habitat. Artificial kelp were effective in recruiting juveniles and small fishes to the site.