Kelp Forests Research Articles

Spatial variability in the structure of fish assemblages associated with Laminaria hyperborea forests in the NE Atlantic

Understanding fish-habitat associations is critical for ecosystem-based approaches to management and conservation. Kelp species, which are estimated to inhabit around 25% of the world's coastline and underpin highly productive and biodiverse ecosystems, are widely recognised as important nursery and foraging habitats for coastal fish species. However, quantitative assessments of fish assemblages within kelp forests are lacking for many regions. Here, we used Baited Remote Underwater Video (BRUV) and Underwater Visual Census (UVC) to quantify fish assemblages in Laminaria hyperborea forests at eight shallow subtidal rocky reefs that spanned 9° of latitude in the United Kingdom (UK). Fish assemblages were a ubiquitous and conspicuous component of kelp forest communities at all sites. BRUV surveys recorded marked regional-scale variability, with latitudinal shifts in assemblage structure and particularly distinct assemblages recorded in southwest England. These patterns were largely due to greater abundances of Pollachius spp. (i.e. saithe and pollock) in northern regions and higher numbers of Gobiusculus flavescens (two-spotted goby) and labrid species (i.e. rock cook, goldsinny and ballan wrasses) in southern regions. Unlike BRUVs, UVC surveys did not detect significant regional-scale variation in assemblage structure but did detect significant site-level differences, highlighting differences between the two techniques. BRUV surveys also recorded clear latitudinal trends in richness, with more taxa recorded at lower latitudes. Fish assemblages in the NE Atlantic have been, and will continue to be, impacted by ocean warming and fishing activities. Greater spatiotemporal coverage of kelp forest surveys and ongoing robust monitoring is needed to better understand and manage future ecological changes.

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.

Impacts of Climate Change on Densities of the Urchin Centrostephanus rodgersii Vary among Marine Regions in Eastern Australia

The urchin Centrostephanus rodgersii is expanding its range southward in eastern Australia, which has been associated with negative ecological impacts, including shifts from kelp forests to barrens. However, limited analyses are available that examine the factors influencing its abundance and distribution across the entirety of this range. Here, we utilise data from 13,085 underwater visual census surveys, from 1992 to 2022, to develop an urchin density model for C. rodgersii across its historical and extending geographical range. We apply this model to examine whether C. rodgersii densities are increasing and to project future urchin densities by 2100 under IPCC climate scenario RCP 8.5. Significant increases in C. rodgersii densities were detected in data for the South-east marine region of Australia, which encompasses Tasmania, Victoria, and the far south coast of New South Wales (NSW) over the last 30 years. In the Temperate East marine region (encompassing Queensland and NSW waters to 36.6° S), however, no significant increases in densities were observed. Future projections indicated that further substantial increases in C. rodgersii densities are likely to occur in the South-east marine region and substantial reductions in most of the Temperate East marine region by 2100. Importantly, results indicate that current and future changes to C. rodgersii densities in Australia vary among marine regions. Therefore, the future ecological impacts of urchins on temperate ecosystems, including the formation of barrens, will also vary among regions. Consequently, management actions will need to differ among these regions, with the South-east marine region requiring mitigation of the impacts of increasing C. rodgersii densities, whereas the Temperate East marine region may need actions to preserve declining C. rodgersii populations.

CubeSats show persistence of bull kelp refugia amidst a regional collapse in California

Bull kelp populations in northern California declined drastically in response to the 2014–2016 marine heatwave, sea star wasting disease, and subsequently large increases in herbivorous purple urchin populations. Despite the regional kelp forest collapse, there were small, remnant populations where bull kelp was able to survive. Moderate resolution satellites (i.e., Landsat) have been important for creating long-term, large-scale time series of bull kelp forests, however, these have been shown to underestimate or entirely exclude refugia due to their low densities and proximity to the coastline. While measurements from Unoccupied Aerial Vehicles (UAV) are spatially detailed, they are temporally limited and difficult to collect over regional scales. The development of CubeSat constellations has enabled a workaround for these tradeoffs, with global imagery available near-daily at meter-scale.We developed a method for mapping bull kelp canopy across the different sensor cohorts in the PlanetScope constellation. This required correcting surface reflectance measurements to account for differences in the spectral response functions among the sensors and leveraging the temporal frequency of PlanetScope data to increase the automation of classifying kelp canopy in imagery with increased noise. Using the PlanetScope derived kelp canopy extents, we identified locations where bull kelp refugia have persisted in northern California. We found that bull kelp refugia occupied about 2% of the total available habitat in the region and about 9.4% of the average canopy area observed prior to 2014. These areas may be critical to the success of kelp forest re-establishment in northern California, which increases their importance for ongoing monitoring, conservation, and restoration efforts.

Prey predictability and preparation versus recovery breathing strategies in European shags Gulosus aristotelis (L.) diving in different habitats

AbstractA recent study on the diving behaviour of European shags (Gulosus aristotelis (L.)) foraging in kelp forests off rocky coasts of Norway suggests surface durations are related only to the duration of the preceding dive, and hence are being used for respiratory recovery. These results contrast with earlier reports concerning shags foraging in highly tidal estuarine waters off the coast of Lundy Island, SW England, where there was a stronger relationship between dive durations and preceding pre‐dive surface durations, suggesting the use of preparatory variation in oxygen loading. These two datasets were collected using different methods, and statistically analysed in quite different ways, so the contrasting results here could be due to different methodologies rather than the ecological differences between the two foraging environments. Here, we re‐analyse the two datasets using similar statistical methods, and we confirm the contrasting results produced by the two datasets. We, therefore, conclude that shag breathing strategies do differ between these two marine environments, presumably reflecting adaptive facultatively plastic responses to differences in predictability of foraging dive durations. Off the Norwegian coast, unpredictable variation in the depth and availability of pelagic prey in complex environments may require more responsive post‐dive respiratory recovery on the surface after each dive. In the more uniform English near‐shore environment, however, pre‐dive preparatory oxygen loading customised to match predictable dive‐to‐dive variation in benthic prey depths and foraging durations, may be more time and energy efficient.

Urchin Gonad Response to Kelp Forest Restoration on the Palos Verdes Peninsula, California

Along the Palos Verdes Peninsula in southern California, high densities of Strongylocentrotus purpuratus (purple sea urchin) have consumed almost all macroalgae on large expanses (61 ha) of rocky reef habitat, creating “urchin barrens.” Mesocentrotus franciscanus (red sea urchin) harvesting comprises an important fishery in the region, as their gonads are sold as a high-value sushi product called “uni.” However, with a lack of macroalgal food resources, urchins in barrens are smaller and exist in a starved state, meaning little, if any, gonad product is available to the fishery. To restore local kelp forests and increase gonad biomass available to the M. franciscanus fishery, beginning in October 2013, S. purpuratus were culled in barrens to a target density of 2 per m2 across 5.2 ha of rocky reef on the Palos Verdes Peninsula. Mesocentrotus franciscanus were collected from urchin barren, restoration, and kelp reference sites from April to November 2014 to compare differences in gonad production among the three site types. Culling S. purpuratus resulted in the recovery of normal seasonal M. franciscanus gonad production throughout the 8-month study. Mesocentrotus franciscanus gonad weights at a given test diameter length in restoration sites were equivalent to, and sometimes exceeded, the gonad production of those from the kelp reference sites. The urchin test length distributions of collected M. franciscanus were consistently smaller at urchin barren sites than at kelp reference sites, while those in restoration sites generally fell in between.

The Hidden Diversity of Temperate Mesophotic Ecosystems from Central Chile (Southeastern Pacific Ocean) Assessed through Towed Underwater Videos

The largely unexplored diversity in temperate mesophotic ecosystems (TME, ~30–150 m depth) has attracted much attention over the past years. However, the number of studies and knowledge of TME diversity and ecology remains limited and geographically restricted. The absence of information on how assemblages vary across environmental gradients and with depth for most regions also limits our capacity to delimit conservation areas and devise management plans effectively. This study focuses on TME from central Chile and describes the depth distribution of reef fishes and benthic invertebrates and algae for the first time. Through the analysis of towed underwater video surveys between 4.7–95.5 m in multiple sites, we show that total reef fish density and richness decrease with depth but increase with local topographic complexity. The depth-related density varies among fish species and trophic groups, and it reverses in the case of Sebastes oculatus, which increases in density with depth. Sponges and gorgonians dominate benthic assemblages below 20 m depth, and brachiopods and anemones increase below 40 and 60 m, respectively. Some of these species form animal forests which, to some extent, replace the shallow-water kelp forests as structural habitat providers. Nevertheless, the reef fish and benthic community do not show a clear structure with depth or across studied sites. We highlight the urgency to intensify and expand the quantitative characterization of these communities, through this and other methodologies, to better define ecological patterns and advance towards conservation plans for TME, including the Souteastern Pacific region.

Roving Diver Survey as a Rapid and Cost-Effective Methodology to Register Species Richness in Sub-Antarctic Kelp Forests

Underwater sampling needs to strike a balance between time-efficient and standardized data that allow comparison with different areas and times. The roving diver survey involves divers meandering and actively searching for species and has been useful for producing fish species lists but has seldom been implemented for benthic taxa. In this study, we used this non-destructive technique to register species associated with kelp forests at the sub-Antarctic Bécasses Island (Beagle Channel, Argentina), detecting numerous species while providing the first multi-taxa inventory for the area, including macroalgae, invertebrates, and fish, with supporting photographs of each observation hosted on the citizen science platform iNaturalist. This research established a timely and cost-effective methodology for surveys with scuba diving in cold waters, promoting the obtention of new records, data sharing, and transparency of the taxonomic curation. Overall, 160 taxa were found, including 41 not reported previously for this area and three records of southernmost distribution. Other studies in nearby areas with extensive sampling efforts arrived at similar richness estimations. Our findings reveal that the roving diver survey using photographs is a good approach for creating inventories of marine species, which will serve for a better understanding of underwater biodiversity and future long-term monitoring to assess the health of kelp environments.

Methanosarcina acetivorans.

Methanosarcina acetivorans is a strictly anaerobic methane-producing archaeon (methanogen) that was isolated from marine sediment beneath a kelp bed in the Sumner branch of Scripps Canyon near La Jolla, California, in 1984. Over the years it has become a primary model to understand the genetics, biochemistry, and physiology of methanogens, microbes that play a critical role in several biogeochemical cycles, impact climate change, and have biotechnological value. The utility of M. acetivorans as a model is due in part to its extensive metabolic versatility.

A Multi-Satellite Mapping Framework for Floating Kelp Forests

Kelp forests provide key habitat on the Pacific Coast of Canada; however, the long-term changes in their distribution and abundance remain poorly understood. With advances in satellite technology, floating kelp forests can now be monitored across large-scale areas. We present a methodological framework using an object-based image analysis approach that enables the combination of imagery from multiple satellites at different spatial resolutions and temporal coverage, to map kelp forests with floating canopy through time. The framework comprises four steps: (1) compilation and quality assessment; (2) preprocessing; (3) an object-oriented classification; and (4) an accuracy assessment. Additionally, the impact of spatial resolution on the detectability of floating kelp forests is described. Overall, this workflow was successful in producing accurate maps of floating kelp forests, with global accuracy scores of between 88% and 94%. When comparing the impact of resolution on detectability, lower resolutions were less reliable at detecting small kelp forests in high slope areas. Based on the analysis, we suggest removing high slope areas (11.4%) from time series analyses using high- to medium-resolution satellite imagery and that error, in this case up to 7%, be considered when comparing imagery at different resolutions in low–mid slope areas through time.

Sunflower sea star predation on urchins can facilitate kelp forest recovery.

The recent collapse of predatory sunflower sea stars (Pycnopodia helianthoides) owing to sea star wasting disease (SSWD) is hypothesized to have contributed to proliferation of sea urchin barrens and losses of kelp forests on the North American west coast. We used experiments and a model to test whether restored Pycnopodia populations may help recover kelp forests through their consumption of nutritionally poor purple sea urchins (Strongylocentrotus purpuratus) typical of barrens. Pycnopodia consumed 0.68 S. purpuratus d-1, and our model and sensitivity analysis shows that the magnitude of recent Pycnopodia declines is consistent with urchin proliferation after modest sea urchin recruitment, and even small Pycnopodia recoveries could generally lead to lower densities of sea urchins that are consistent with kelp-urchin coexistence. Pycnopodia seem unable to chemically distinguish starved from fed urchins and indeed have higher predation rates on starved urchins owing to shorter handling times. These results highlight the importance of Pycnopodia in regulating purple sea urchin populations and maintaining healthy kelp forests through top-down control. The recovery of this important predator to densities commonly found prior to SSWD, whether through natural means or human-assisted reintroductions, may therefore be a key step in kelp forest restoration at ecologically significant scales.

‘Hanging gardens’—comparing fauna communities in kelp farms and wild kelp forests

A growing need for food is causing increased interest for seaweed farming globally. This requires the knowledge of the industry’s effects on the marine environment. We therefore aimed to explore the communities hosted by a kelp farm compared to that of wild kelp forests. The study was performed in mid-western Norway. Kelp associated fauna were collected from farmed kelp (Saccharina latissimaandAlaria esculenta), in wild kelp forests (S. latissima,A. esculenta, andLaminaria hyperborea), and from fauna traps in the water column. The study showed that the kelp farm had lower taxa abundance and richness and a lower biodiversity than the wild kelp forests. Nonetheless, the farmed kelp hosted many associated species, with communities different from what was found on ropes without kelp (i.e., in the water column). The fauna communities among the farmed kelp were more similar to what was found in the wildL. hyperboreakelp forest than to its wild counterparts. The difference between the fauna communities of ‘old’ and ‘young’ farmed kelp (grown for 3 and 7 months, respectively) was not significant, but the fauna was dominated by the isopod speciesIdotea pelagicain the young forest and by amphipods, mainly belonging to the genusCaprella, in the older. The study contributes to our knowledge of kelp farms’ ecological role in the marine environment, which is of importance for today’s management as well as for ensuring a sustainable future development of the kelp farming industry.

Small-scale spatiotemporal thermal regimes drive patterns of zooplankton abundance in a kelp forest

During internal tidal forcing, high-frequency water column temperatures and zooplankton abundances were measured within and at the outer edge of a Giant Kelp Forest at two depths. Although the sampling sites were only separated by 300m, differences occurred in their thermal regimes and in their zooplankton abundance, distribution, and temperature relationships. Dominant organisms at both sites included copepods and bryozoan cyphonautes. Outside of the kelp forest, the water column was more stratified, with distinct alternating cold and warm periods defined by abrupt thermal fronts indicative of internal wave phases. Lower zooplankton abundances and fewer taxa (only 31) were detected, with more cyphonautes and copepods found in the deeper strata and during the cold phase of internal waves. Inside the kelp forest, on the other hand, the water column was less stratified and less variable over time, with no clear alternating internal wave phases. An order of magnitude greater zooplankton abundance occurred with more taxa (54) identified and more cyphonatues and copepods found in the surface strata. At both sites, abundances of copepods increased with high frequency cooling in the deeper strata, whereas near the surface they showed the reverse pattern, increasing during warming. Across sites, cyphonautes decreased outside of the kelp forest while they increased within the kelp forest. The patterns detected across depths, across sites, and related with high frequency thermal variability suggest complex forcing of zooplankton abundances by alternating shoaling and sinking of the thermocline related with internal waves. These results emphasize the small-scale spatiotemporal biophysical complexity in nearshore waters and contribute to the understanding of nearshore plankton dynamics related with internal wave forcing mechanisms in Giant Kelp Forest environments.

Giant Kelp Forest Resilience to Ocean Warming; Historical and Modern Systems

Giant kelp forests of the North Pacific are iconic among cool temperate marine communities. They are also amongst the most productive marine ecosystems, harboring significant biodiversity and supporting coastal economies. The fate of these systems over the next eight decades is uncertain, given the variance of outcomes for global warming scenarios and the complexities of ecological forecasting. There is a growing consensus that giant kelp will be susceptible to warming, leading to a decline of the communities. Kelp forest dynamics, however, are also controlled by biotic interactions. In the North Pacific, the main biotic factors today are kelp herbivory, especially by grazing sea urchins, and predatory control of the urchins, particularly by sea otters and sunflower sea stars. A recent study demonstrated that as late as the 18th century, the now extinct mega herbivore Steller’s sea cow, an obligate kelp browser, had a significant impact on North Pacific kelp forest dynamics. Mathematical models comparing the historical community to modern ones indicated that the sea cow would have increased forest resilience against reductions of predation of urchins caused by multiple types of perturbation. In addition to epidemics and temperature anomalies, it is expected that global temperatures will increase 2-4 degrees Celsius by the year 2100. Here we use the mathematical models to explore forest dynamics under various warming scenarios, including the changing impacts of epidemics and the frequency and intensity of warming anomalies. Preliminary results suggest that in contrast to a stable temperature regime, warming to 4 degrees increases chaotic dynamics, extinction of both sea urchins and sunflower sea stars, and abundance of understory algae. Those results also suggest that chaos and algal increase would be lessened in the presence of the extinct herbivore. These findings bear implications for future kelp forest management, conservation, and human economic exploitation.

Steller’s Sea Cow and Kelp Forest Regeneration in the North Pacific

Modern ecosystems are almost universally degraded relative to their past counterparts, from the Pleistocene to the present day. Thus, modern ecosystems may serve as poor guides to conservation actions. Conservation paleobiology is well-suited to address this challenge through enhanced understanding of systems dynamics during past periods of greater species and functional diversity, abundances, and resilience. However, past and present ecosystem dynamics must be integrated to model the future impacts of conservation actions. Here we propose a three-step, Past-Present-Future (PPF) methodology rooted in mathematical modeling. First, construct a model of primary species and interactions of the present-day ecosystem, including biotic and abiotic components. Second, integrate historical and/or paleontological data into the model to investigate past states and processes of the ecosystem, with an emphasis on critical elements (e.g., ecological engineer species) that are no longer present. Third, integrate analyses from the first two steps to predict putative future dynamics and states, and use these to make testable predictions regarding specific conservation interventions. We illustrate this approach with a study investigating impacts of the now-extinct Steller’s sea cow on north Pacific giant kelp forests. The model indicates that the historical system was distinct from the modern, with differing abundances of giant kelp and understory algae. Furthermore, the familiar kelp-dominated state is metastable, capable of rapid transitions to an urchin-dominated state if perturbed by extreme hydrodynamic events, disease-driven reductions of seastar predation, or disease coupled to extreme warming events. We explore the possibility of increasing the resilience of modern forests by artificially recreating at least some of the ecological impacts of sea cows, accounting for metabolic requirements, estimates of abundance based on recent analyses of ancient DNA, and trophic impact.

Structural diversity: a digital revolution

One of the fundamental rules in biology and ecology is that structure determines function. At a microscale, the transmissibility of COVID-19 is related to the unique structure of the novel coronavirus's trimeric spike protein. At a macroscale, the success of early human settlement along the west coast of North America during the Holocene is likely associated with the rich resources provided by the diverse structures of kelp forests. Until recently, research on ecosystem structure and diversity has lagged, due primarily to a lack of tools to measure these components effectively and accurately. For instance, scientists studying deciduous forests have relied on stem size and leaf area as proxies of forest structure to predict ecosystem functions. However, these traditional, proxy-based metrics are laborious to collect, logistically challenging to assess at large scales, and fail to capture other critical aspects of structural diversity such as canopy depth and complexity, both of which provide better predictions of ecosystem functions and processes as compared to their conventional counterparts. Fortunately, innovations in digital technology and data science are converging to yield a wide range of new research capabilities. As demonstrated by the papers in this Special Issue, ecologists are starting to embrace these promising advances, unlocking opportunities to understand structural diversity. We now have a robust suite of sensors that can be deployed on different platforms and used to map and measure three-dimensional (3D) structures in both terrestrial and aquatic systems, across a wide range of scales and resolutions. For example, modern single-photon lidar can provide wall-to-wall, high-resolution, 3D point cloud data in less than one hour for an area of over 10,000 ha, allowing individual tree-level measurement. Spanning large geographic regions, these unprecedented 3D data will enable investigations of fundamental ecological questions (eg macroscale patterns, scaling) that traditional plot-based approaches cannot. As with other innovations, however, these structural data also bring unencountered challenges. To take full advantage of ecology's digital advances, we argue that the following challenges must be addressed. The first is the necessity to ensure truly transdisciplinary collaboration. Although recognized for decades, the demand for such collaboration has never been greater in 3D structural diversity enabled ecology, especially at its current early stages of development. Most of the skillsets essential to harnessing and realizing the potential of these new technologies currently lie in disciplines beyond ecology and the environmental sciences. We need expertise from aviation technology for stable and safe data acquisition, engineering solutions for sensor integration, geomatics for data registration, computer science for data integration and segmentation, graphic design for visualization, information science for managing data and ensuring fair access, and social science for understanding societal implications and unintended consequences, to name a few. The quickest way for ecologists and environmental scientists to incorporate these research skills into their own work is through collaboration. The second challenge is embracing novel computational platforms (eg super computers, cloud computing) and approaches (eg machine learning and artificial intelligence). When covering large spatial extents, these 3D data often range from gigabytes to terabytes to petabytes in size. Therefore, advanced computing power and algorithms are required to handle them. Third, to better utilize these data, investigators will have to shift from traditional hypothesis-driven approaches to data-driven approaches or to a hybrid of the two. As these 3D data can generate hundreds of variables measuring different aspects of ecosystem structure, making sense of the data, especially when combined with other climatic and geophysical datasets, can be daunting or nearly impossible. Such massively multivariate datasets can quickly overwhelm traditional process-based modeling approaches. When deployed by knowledgeable analysts, machine learning approaches – whether data driven or domain knowledge guided – may reveal insights into ecosystem patterns and processes. Lastly, there is a pressing need to educate our next generation to embrace these digital advances. New data-oriented skills such as acquisition, visualization, analysis, and management of large datasets must become essential parts of ecological training. Consideration of structural diversity is foundational to our understanding of ecological systems. Consequently, advances in 3D data acquisition and analytics will likely reshape our understanding of ecology. Adopting these emerging digital technologies will enable the next generation of ecologists to gracefully operate a fleet of sensors to measure ecosystems and swim freely in the resulting ocean of data.

Climate change threatens unique evolutionary diversity in Australian kelp refugia

Climate change has driven contemporary decline and loss of kelp forests globally with an accompanying loss of their ecological and economic values. Kelp populations at equatorward-range edges are particularly vulnerable to climate change as these locations are undergoing warming at or beyond thermal tolerance thresholds. Concerningly, these range-edge populations may contain unique adaptive or evolutionary genetic diversity that is vulnerable to warming. We explore haplotype diversity by generating a Templeton–Crandall–Sing (TCS) network analysis of 119 Cytochrome C Oxidase (COI) sequences among four major population groupings for extant and putatively extinct populations only known from herbarium specimens of the dominant Laminarian kelp Ecklonia radiata in the south-western Pacific, a region warming at 2–4 times the global average. Six haplotypes occurred across the region with one being widespread across most populations. Three unique haplotypes were found in a deep-water range-edge population off Moreton Island, Queensland, which likely represents both a contemporary and historic refuge during periods of climatic change. Hindcasting E. radiata cover estimates using extant data, we reveal that this region likely supported the highest kelp cover in eastern Australia during the last glacial maximum. The equatorward range edge, deep-water kelp populations off Moreton Island represent a genetically diverse evolutionary refuge that is currently threatened by warming and requires prompt ex-situ conservation measures.

Archaeological and stable isotope data reveal patterns of fishing across the food web on California’s Channel Islands

How do human communities integrate within food webs? Studies characterizing the historical flow of energy among people and local environments can yield important insights into managing sustainable ecosystems. Here, we combine zooarchaeological, bulk tissue, and compound-specific stable isotope data from late Holocene Santa Rosa Island to investigate the ecological role of people within a southern California nearshore marine ecosystem. We show people foraged in diverse marine habitats, including kelp forests and pelagic waters, and consumed a wide range of species. However, zooarchaeological results reveal >50% of recovered fish remains came from presumed kelp forest carnivores of mid-trophic level (3.0–4.0) such as surfperches and rockfishes. Local fishing strategies thus did not involve the preferential removal of large-bodied, high trophic level species – a pattern known as “fishing down the food web” which has been documented in modern commercial fisheries and results in the collapse of marine ecosystems. Essential amino acid δ13C analysis revealed that the historical fish community relied on basal resources from kelps and phytoplankton. This coupling of benthic and pelagic energy sources suggests late Holocene coastal food webs in the region were in a relatively stable configuration immediately prior to first European arrival. This stability likely contributed to sustaining densely populated Chumash settlements, intensive fisheries, and high local faunal diversity. Our findings provide important pre-industrial data for marine ecosystems and document some of the mechanisms behind the intensive, yet sustainable long-term fisheries of the Island Chumash.

Seaweed restocking along the Chilean coast: History, present, and inspiring recommendations for sustainability

Several seaweed species are commercialized worldwide both due to high demand for food and feed and as a raw material for the extraction of phycocolloids such as agar, carrageenan, and alginates that are used broadly in the food, cosmetic, and pharmaceutical industries. Chile is the world’s leading marine seaweed biomass producer when it comes to the exploitation of natural kelp beds. This extraction pressure has persisted for decades and has resulted in a reduction in natural stocks along the benthic ecosystems of the Chilean coast. Over the last three decades, several strategies aimed at restoring seaweed stocks have been implemented (i.e., sexual and asexual reproduction, the use of spore-type propagules or fragments of thalli, and entire thallus transplants). Success rates have varied, but the biological feasibility of such strategies has been demonstrated for several species. However, technological improvements must be achieved to move from small-scale, pilot experiments to cost-effective restocking strategies that are easy to transfer to fisher communities and another end-user, scalable to marine field conditions, and socio-ecologically sustainable. Researchers in other geographic areas have explored similar pathways for developing kelp restocking strategies and have tackled the research gaps regarding its massification. This work summarizes the research activities carried out in recent decades in the search for sustainable strategies to restore algal stocks in Chile.

Patterns and drivers of benthic macroinvertebrate assemblages in the kelp forests of southern Patagonia.

The kelp forests of southern Patagonia have a large diversity of habitats, with remote islands, archipelagos, peninsulas, gulfs, channels, and fjords, which are comprised of a mixture of species with temperate and sub-Antarctic distributions, creating a unique ecosystem that is among the least impacted on Earth. We investigated the distribution, diversity, and abundance of marine macroinvertebrate assemblages from the kelp forests of southern Patagonia over a large spatial scale and examined the environmental drivers contributing to the observed patterns in assemblage composition. We analyzed data from 120 quantitative underwater transects (25 x 2 m) conducted within kelp forests in the southern Patagonian fjords in the Kawésqar National Reserve (KNR), the remote Cape Horn (CH) and Diego Ramírez (DR) archipelagos of southern Chile, and the Mitre Peninsula (MP) and Isla de los Estados (IE) in the southern tip of Argentina. We observed rich assemblages of macroinvertebrates among these kelp forests, with a total of 185 unique taxa from 10 phyla and 23 classes/infraorders across the five regions. The number of taxa per transect was highest at IE, followed by MP, CH, and KNR, with the lowest number recorded at DR. The trophic structure of the macroinvertebrate assemblages was explained mostly by wave exposure (28% of the variation), followed by salinity (12%) and the KNR region (11%). KNR was most distinct from the other regions with a greater abundance of deposit feeders, likely driven by low salinity along with high turbidity and nutrients from terrigenous sources and glacial melt. Our study provides the first broad-scale description of the benthic assemblages associated with kelp forests in this vast and little-studied region and helps to establish baselines for an area that is currently lightly influenced by local anthropogenic factors and less impacted by climate change compared with other kelp forests globally.