New records of Microzonia velutina (Syringodermatales, Ochrophyta) in Isla Grande de Tierra del Fuego in the sub-Antarctic region

Preface Acknowledgments Introduction PART I. THE BIOLOGY OF GIANT KELP 1. Introduction to Giant Kelp Forests Worldwide 2. The Structure, Function, and Abiotic Requirements of 3. The Abiotic Environment 4. Demography, Dispersal, and Connectivity of Populations PART II. THE GIANT KELP ECOSYSTEM 5. Giant Kelp Communities 6. Detached Giant Kelp Communities, Production, and Food / Control Webs 7. Facilitative and Competitive Interactions in Giant Kelp Forests 8. Grazing in Kelp Communities 9. Predation and Trophic Cascades in Kelp Communities PART III. HUMAN USAGE, MANAGEMENT, AND CONSERVATION 10. Anthropogenic Effects on Kelp Forests 11. Human Usage of Giant Kelp and Kelp Forest Organisms 12. Marine Protected Areas and Fisheries Effects PART IV. GLOBAL CHANGE AND THE FUTURE 13. Global Change 14. Giant Kelp Forests: Conclusions and Final Thought Afterword References Index

Giant kelp-associated variation in coastal seawater chemistry across contrasting sites in Chile and Tasmania.

Amphipods are abundant in marine ecosystems worldwide and are important as prey and as consumers of macrophytes and detritus in food webs. Due to the spatially complex and dynamic nature of giant kelp (Macrocystis pyrifera) forests, assessment of the abundances of giant kelp and amphipods through time and space should provide insight into their potential interactions within the system. In an extensive field study within the surface canopy of giant kelp, the abundance of amphipods was quantified on artificial substrates at an array of 18 sites within kelp forests along Point Loma, California, USA, from July to October 2009 and 2010. Biomass of giant kelp canopy was estimated using remotely sensed imagery, and the spatial synchrony (autocorrelation through time) of kelp canopy was compared with synchrony of caprellid and non-caprellid amphipods. Caprellids exhibited high spatial synchrony that did not decrease with distance, while non-caprellids were synchronous on local scales, indicating high spatial heterogeneity in abundance through time. Gammarids showed a rapid exponential decrease in synchrony within the first 550 m that was consistent with synchrony of giant kelp. This suggests a local-scale biotic link between non-caprellids and giant kelp canopy, whereas caprellid synchrony is more likely to be influenced by regional-scale environmental variables. Caprellids and other amphipods are important prey resources for common kelp forest fishes, so these differences may in turn affect the spatial distributions of these predators. Moreover, excretion by amphipods may be an important source of nitrogen to giant kelp during periods of nitrogen limitation.

The effects of seascape pattern on algal patch structure, sea urchin barrens, and ecological processes

Nutrient distribution and propagule dispersal within Giant kelp (Macrocystis pyrifera) forests are significantly influenced by turbulence. In-situ measurements of turbulence within giant kelp forests are limited and driving mechanisms are primarily informed by controlled-flume experiments. This study investigates relationships between currents, surface gravity waves, and turbulence within a kelp forest through deployment of moored instrumentation and kelp surveys in Stillwater Cove, California during summer of 2022. Oceanographic conditions were primarily driven by coastal upwelling and a semi-diurnal internal tide, which was associated with cooling events and enhanced onshore velocity within the kelp forest during rising tides. Estimates of gradient Richardson numbers and kelp Reynolds numbers indicate that shear-instabilities are rare, while enhanced bottom velocities could consistently generate turbulent kelp wake. Turbulent kinetic energy dissipation rate (ε) spans a range of 1.9 x 10-8 to 8.0 x 10-7 m2/s3 and is positively correlated with onshore velocities, but uncorrelated with offshore velocities. This asymmetrical pattern may be triggered by cooling events that generate turbulence through interactions with dense kelp and rough bottom substrate. Models of submerged vegetation wake production and bottom boundary layer turbulent kinetic energy were compared to observed values of ε to assess hypothetical kelp and bed drag coefficients. Study results indicate that kelp density is important for future studies of nutrient distribution and propagule dispersal.

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 485:75-89 (2013) - DOI: https://doi.org/10.3354/meps10329 Spatial patterns of invertebrate settlement in giant kelp forests Dana N. Morton1,2,*, Todd W. Anderson1 1Department of Biology and Coastal & Marine Institute, San Diego State University, San Diego, California 92182-4614, USA 2Present address: Department of Ecology, Evolution, and Marine Biology, University of California Santa Barbara, Santa Barbara, California 93106, USA *Email: dana.morton@lifesci.ucsb.edu ABSTRACT: Settlement of kelp-associated organisms may vary as they are delivered to (and through) giant kelp (Macrocystis pyrifera) forests, with implications for local population dynamics and community structure. Previous work suggests that settlement of invertebrates with long pelagic durations would be reduced as they move from an offshore environment toward the interior of kelp forests due to dampened current flow and reduced larval delivery. We evaluated spatial variation in settlement across giant kelp forests in an extensive field study conducted over 2 yr. We collected and sorted >36000 settling organisms and had sufficient data to explore patterns in detail for 8 taxa. Orthogastropods (snails) were the most common invertebrates and exhibited a pattern of declining settlement from the outer (seaward) to inshore edge of kelp forests. Inverse patterns were observed for Crepidula spp. and carideans, and other abundant taxa (non-sessile polychaetes and pectinids) showed spatial structure that differed regionally and between years. Other taxa failed to exhibit significant spatial variation in settlement. In general, settlement was lower near the sea floor than in the upper water column, and similar across locations for most groups. For some taxa, spatial variation was more apparent when the magnitude of settlement was relatively low, which may suggest that kelp forests become ‘saturated’ with larvae during pulses of high settlement. Our results are in contrast to previous predictions, as we observed high settlement in the interior for several species with long pelagic durations. For taxa that settled evenly across kelp-forested reefs, differential distributions of adults may be attributed to post-settlement processes. The patterns we observed here warrant additional study to address potential mechanisms for differential settlement. KEY WORDS: Settlement · Invertebrates · Giant kelp forests · Larval filtering · Macrocystis pyrifera · Biogenic structure Full text in pdf format Supplementary material PreviousNextCite this article as: Morton DN, Anderson TW (2013) Spatial patterns of invertebrate settlement in giant kelp forests. Mar Ecol Prog Ser 485:75-89. https://doi.org/10.3354/meps10329 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 485. Online publication date: June 27, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

We present findings from two sets of measurements that quantified currents around and over the full extent of a giant kelp (Macrocystis pyrifera) forest located at Mohawk Reef, Santa Barbara, California. Velocities were damped inside this 200‐m X 300‐m forest, but not to the extent reported for larger (kilometer‐scale) kelp beds, suggesting that alongshore currents may play a greater role in exchange than has often been assumed. Secondary flow features that bear on the performance of forest organisms were observed, including a region along the forest’s outer boundary where velocities exceeded incident speeds by up to 200%. An offshore current on the order of 1 cm s−1 developed within the kelp bed, likely due to pressure gradients established across the forest coupled with topography. Wake recirculations that might have facilitated leeward retention of waterborne subsidies were not apparent. Calculations suggest that kelp beds can interact with (and thus potentially filter) substantial portions of impinging waters; in our study, 40–90% of arriving waters entered the upstream end, and 20–70% reached the center of the forest. Seasonal changes in the size and density of the forest modified the levels of flow damping and filtration. The sum of these effects suggests potential influences on organisms throughout the forest community.

Benthic macroalgae (including brown macroalgae or kelp) constitute one of the largest contributors to coastal primary production, but their ability to store and sequester carbon remains uncertain. Here, we use a numerical model of the flow/kelp interactions to study how tidal currents interact with an idealised numerical model of a giant kelp (Macrocystis pyrifera) forest, intending to better understand the potential for kelp growth in nutrient-limited conditions and the export of important tracers such as dissolved organic carbon. We calibrate and test our model using observations of currents within and surrounding a kelp forest in Southern California. By varying the density of kelp in our model, we find that there is a kelp density that maximises the export of tracer released from the kelp forest. Since the tracer advection/diffusion equation is linear with respect to the tracer concentration, the same kelp density corresponds to the maximum uptake for a tracer with a constant far-field concentration. The density at which this maximum occurs coincides with the density typical of natural kelp forests, where kelp growth may be limited by the uptake of dissolved nutrients from the surrounding water. Additionally, the drag induced on the tidal currents by the kelp forest results in a mean circulation through the kelp forest and a mean displacement of the kelp forest canopy.

It has been hypothesized that the high diversity of giant kelp forests is due primarily to the provision of energy and habitat by the giant kelp (Macrocystis pyrifera). In this article, I use a 19-year-long kelp forest-monitoring data set from the Channel Islands National Park (a) to identify associations between subtidal species and forested or deforested habitats, (b) to generate an idealized food web for Southern California giant kelp forests in order to identify the primary conduits of energy flow through the system, and (c) to determine changes in the diversity and complexity of this food web due to localized giant kelp deforestation. A total of 275 common species were observed in the park between 1982 and 2000, of which 36% occurred significantly more often in kelp-forested areas than in deforested areas (that is, sea urchin barrens); 25 species were found exclusively in forested areas. Most of these associations were clearly identified as trophic and/or structural associations with giant kelp itself. The producer level of the food web was diverse, although giant kelp apparently represents the greatest single source of fixed carbon through either direct grazing or the production of phytodetritus. Primary, secondary and tertiary consumer levels were also represented by numerous species, and generalist consumers were common. With deforestation, the source of primary production shifts from primarily kelps to ephemeral microalgae, macroalgae, and phytoplankton. These results support the reliance of giant kelp forest food-web structure and diversity on the presence of the forest itself.

Giant kelp, Macrocystis pyrifera (order Laminariales), occurs across the temperate coasts of the Northern and Southern Hemispheres and is at high risk from ocean warming. Few giant kelp forests remain across the Southeast Australian shelf, and some sites are currently under active restoration. Genomic resources can greatly aid in the conservation of remnant populations and enhance restoration efforts. Reference genomes are a fundamental resource as they are either prerequisites for, or substantially improve, many analyses used in conservation genomics. A single reference genome is available for giant kelp, assembled from a Californian haploid specimen. However, increasing evidence of genetic divergence between Northern and Southern Hemisphere populations highlights the need for regionally representative reference genomes. We present two genome assemblies from the vegetative tissue (diploid sporophyte) of Australian giant kelp specimens. We performed de novo genome assembly using long-read sequencing (PacBio HiFi and ONT R10.4 Simplex) and used the ONT reads for scaffolding, assembling 98-99% of the genomes into 35 pseudo-chromosomes. Genome sizes ranged from 528 to 534 Mbp, with BUSCO completeness of 96-97% and QV scores of 51-52. Functional annotation identified 17,330 - 17,832 genes in the Australian assemblies. Genomic divergence between Australian and Californian genomes was seven-fold greater than between Australian genomes (1.5% vs. 0.2%), supporting a northeast-southwest Pacific genetic divergence. Differences in gene ontology enrichment patterns were also observed between Australian and Californian genomes, reflected by differing patterns of enrichment in gene ontologies linked to energy metabolism, proteostasis and stress responses. These two new genome assemblies will serve as valuable resources for ongoing research into Australian giant kelp genetics, while providing the basis for genomics-guided conservation and restoration of remnant giant kelp forests in Australia.

Free-living and particle-associated prokaryote metabolism in giant kelp forests: Implications for carbon flux in a sub-Antarctic coastal area

Three decades of variability in California's giant kelp forests from the Landsat satellites

Recent discussions on scaling issues in ecology have emphasized that processes acting at a wide range of spatial and temporal scales influence ecosystems and thus there is no appropriate single scale at which ecological processes should be studied. This may be particularly true for environmental disturbances (e.g. El Niño) that occur over large geographic areas and encompass a wide range of scales relevant to ecosystem function. However, it may be possible to identify the scale(s) at which ecosystems are most strongly impacted by disturbances, and thus provide a measure by which their impacts can be most clearly described, by assessing scale-dependent changes in the patterns of variability in species abundance and distribution. This, in turn, may yield significant insight into the relative importance of the various forcing factors responsible for generating these impacts. The 1997-98 El Niño was one of the strongest El Niños ever recorded. I examined how this event impacted giant kelp populations in the northeast Pacific Ocean at 90 sites ranging from central Baja California, Mexico to central California, USA. These sites spanned the geographic range of giant kelp in the Northeast Pacific and were surveyed just before, immediately following, several months after, more than 1 year after, and nearly 2 years after the El Niño. I used a hierarchical sample design to compare these impacts at five spatial scales spanning six orders of magnitude, from a few meters to more than 1,000 km. Variance Components Analyses revealed that the El Niño shifted control over giant kelp abundance from factors acting at the scale of a few meters (local control) to factors operating over hundreds to thousands of kilometers (regional control). Moreover, El Niño resulted in the near-complete loss of all giant kelp throughout one-half of the species' range in the northeast Pacific Ocean. Giant kelp recovery following El Niño was far more complex and variable at multiple spatial scales, presumably driven by numerous factors acting at those scales. Recovery returned local control of giant kelp populations within 6 months in southern California, and within 2 years in Baja California.

IntroductionGlobal degradation of natural ecosystems demands urgent action to stem losses and, where possible, identify opportunities for scalable restoration. Giant kelp forests, formed by Macrocystis pyrifera, have declined by ~95% along eastern Tasmania in recent decades, with limited propagule supply constraining recovery. Direct interventions to restore giant kelp have been attempted here since the 1990s, although attempts have been constrained by methodological and logistical limitations, underscoring the challenges of scaling restoration in subtidal marine environments.ObjectivesThis study details the methodological development of a rapid and forest‐scale in situ approach to reseed threatened giant kelp forests that have declined.MethodsHere we provide an overview of the “holdfast‐graft” method, as a forest‐scale technique to reseed reefs with mass‐produced hatchery‐reared giant kelp sporophytes seeded to twine. Taking inspiration from true grafting of terrestrial vascular plants, we apply an analogous approach of effectively binding the equivalent of a “scion” (i.e., hatchery‐reared giant kelp sporophytes) to a “root‐stock” (i.e., holdfast stubs of other common seaweed species). By comparing rates of kelp sporophyte attachment between twine seeded to holdfast stubs and directly to boulders, as well as seeded gravel, we evaluate the effectiveness of this method.ResultsWe reveal a 40‐fold higher rate of kelp sporophyte attachment to the reef when twine was wrapped around holdfast stubs compared to twine wrapped over boulders or deployments of hatchery seeded‐gravel methods. Refinement of the “holdfast‐graft” method led to targeted wrapping of short 60‐cm seeded twine lengths directly to individual holdfast stubs, enabling rapid and forest‐scalable deployment by divers.ConclusionsThe “holdfast‐graft” method represents an efficient and scalable method for out‐planting giant kelp.

Foundation species structure communities, promote biodiversity, and stabilize ecosystem processes by creating locally stable environmental conditions. Despite their critical importance, the role of foundation species in stabilizing natural communities has seldom been quantified. In theory, the stability of a foundation species should promote community stability by enhancing species richness, altering the population fluctuations of individual species, or both. Here we tested the hypothesis that the stability of a marine foundation species, the giant kelp Macrocystis pyrifera, increased the stability of the aggregate biomass of a phylogenetically diverse assemblage of understory algae and sessile invertebrates that compete for space beneath the giant kelp canopy. To achieve this goal, we analyzed an 18-yr time series of the biomass of giant kelp and its associated benthic community collected from 32 plots distributed among nine shallow reefs in the Santa Barbara Channel, USA. We showed that the stability of understory algae and sessile invertebrates was positively and indirectly related to the stability of giant kelp, which primarily resulted from giant kelp's direct positive association with species richness. The stability of all community types was positively related to species richness via increased species stability and species asynchrony. The stabilizing effects of richness were three to four times stronger when algae and invertebrates were considered separately rather than in combination. Our finding that diversity-stability relationships were stronger in communities consisting of species with similar resource requirements suggests that competition for shared resources rather than differential responses to environmental conditions played a more important role in stabilizing the community. Increasing threats to structure-forming foundation species worldwide necessitates a detailed understanding of how they influence their associated community. This study is among the first to show that dampened temporal fluctuations in the biomass of a foundation species is an important determinant of the stability of the complex communities it supports.