Diel and tidal rhythms drive fish acoustic communities in a European kelp forest

Birds produce diverse acoustic signals, with coexisting species occupying distinct “acoustic niches” to minimize masking, resulting in overdispersion within acoustic space. In tropical regions of the world, an influx of migrants from temperate regions occurs during winter. The effects of these migrants on acoustic community structure and dynamics remain unstudied. Here, I show that in a tropical dry forest bird community occurring within an urban area in India, the influx of winter migrants is accompanied by a change in species composition of the acoustic community. However, in spite of this, the acoustic community remains overdispersed in acoustic niche space. The winter community of vocal birds at this study site additionally exhibits lower energy in the 4–7 kHz frequency bands (consistent with species singing less continuously), as well as lower phylogenetic diversity. My data are thus indicative of seasonal turnover in acoustic communities but suggest that acoustic niches and community structure are stable across seasons. Migrants occupy similar regions of acoustic space as residents and are relatively closely related to some of these species. Their arrival, therefore, leads to greater phylogenetic clustering in the winter and thus lower phylogenetic diversity, although the acoustic community remains overdispersed. Studying seasonal dynamics of acoustic communities thus provides valuable insight into assembly processes, as well as a potential framework for long-term monitoring of urban ecosystems.

In marine ecosystems, biodiversity, biological rhythms, and macrofaunal community behaviors are fundamental to assess the cumulative impact of environmental and human pressures but they remain understudied. Ecoacoustics offers a promising approach to fill these gaps: it analyzes biological (biophony), abiotic (geophony), and anthropogenic (anthrophony) sounds to provide high temporal-resolution insights. Marine forests (e.g., kelp, seagrass meadows) are essential habitats, that rank among the most productive and biodiversity-rich ecosystems and provide billions of dollars of essential ecosystem services to humanity. However, with less than 3% of ecoacoustics studies, they remain largely underrepresented. Despite the potential of ecoacoustics in acquiring information on the cryptic species of dense habitats, the biophonic component of European marine forests is currently poorly or not documented.Here we describe the biogeography of fish acoustic communities of three different marine forests (kelp forest, zostera and posidonia seagrass meadow) at the European scale (Atlantic and Mediterranean coasts). During the European TREC expedition, continuous sound recordings were conducted over 48-72h at 17 sites across Europe.Using a standardized sound classification method, this biogeographic study provides the first detailed description of fish acoustic communities in European marine forests. We analyzed the composition and parameters of acoustic communities (abundance, richness, biodiversity indices) and revealed inter-habitat, intra- and inter-site variability. Acoustic communities were significantly distinct between habitats, with greater site variability within Zostera meadows, compared to kelp forests, suggesting differences in connectivity in seagrass. Site characteristics and sampling periods were considered, and relationships between acoustic communities, taxonomic diversity, diel variation and environmental variables (e.g., light, temperature) were examined. Our findings offer an unprecedented large-scale view of fish acoustic community composition in underexplored European habitats. This work reveals that acoustic biodiversity can contribute to habitat biogeography and infer information on the invisible, hidden animal assemblages, their dynamics and responses to environmental changes.

Kelp forests provide habitat for many species, but it remains uncertain whether specific kelp forest types support distinct biodiversity. Surface canopy-forming giant kelp (Macrocystis pyrifera) forests in Tasmania, Australia, have declined significantly due to climate change, and have been widely replaced by forests dominated by smaller stipitate kelps like Ecklonia radiata. However, there is limited knowledge of the community composition of Macrocystis forests and how this may differ from the stipitate kelp forest community. Underwater visual census surveys were conducted of the fishes and macroinvertebrates (> 2.5 cm length) in remnant Macrocystis forests in south-eastern Tasmania, and in adjacent stipitate kelp forests. 18 sites (9 of each forest type) were surveyed across two regions during the period of peak growth and canopy cover (i.e. winter-spring). Faunal community composition varied little between forest types, although Macrocystis forests supported more than double the abundance and biomass of mobile fishes, while cryptic fishes differed by forest type depending on region. Macroinvertebrate assemblages did not differ between forest types nor regions. Thus, for the taxa and time period examined, Tasmanian Macrocystis and stipitate kelp forests supported mostly similar faunal communities. Kelp forest communities showed spatial variation and were also likely influenced by a variety of other habitat characteristics, such as the relatively small patch sizes and/or ephemeral state of the remnant Macrocystis forests. Quantifying the community structure of these endangered communities informs the ecological changes that have occurred and will serve as an important reference for ongoing conservation and restoration activities.

The recovery of predators has the potential to restore ecosystems and fundamentally alter the services they provide. One iconic example of this is keystone predation by sea otters in the Northeast Pacific. Here, we combine spatial time series of sea otter abundance, canopy kelp area, and benthic invertebrate abundance from Washington State, USA, to examine the shifting consequences of sea otter reintroduction for kelp and kelp forest communities. We leverage the spatial variation in sea otter recovery to understand connections between sea otters and the kelp forest community. Sea otter increases created a pronounced decline in sea otter prey-particularly kelp-grazing sea urchins-and led to an expansion of canopy kelps from the late 1980s until roughly 2000. However, while sea otter and kelp population growth rates were positively correlated prior to 2002, this association disappeared over the last two decades. This disconnect occurred despite surveys showing that sea otter prey have continued to decline. Kelp area trends are decoupled from both sea otter and benthic invertebrate abundance at current densities. Variability in kelp abundance has declined in the most recent 15years, as it has the synchrony in kelp abundance among sites. Together, these findings suggest that initial nearshore community responses to sea otter population expansion follow predictably from trophic cascade theory, but now, other factors may be as or more important in influencing community dynamics. Thus, the utility of sea otter predation in ecosystem restoration must be considered within the context of complex and shifting environmental conditions.

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 279:129-139 (2004) - doi:10.3354/meps279129 Effects of marine reserves and urchin disease on southern Californian rocky reef communities Michael D. Behrens1,*, Kevin D. Lafferty2 1Department of Ecology, Evolution and Marine Biology, and 2United States Geological Survey, Western Ecological Research Center, c/o Marine Science Institute, University of California at Santa Barbara, Santa Barbara, California 93106, USA *Email: behrens@lifesci.ucsb.edu ABSTRACT: While the species level effects of marine reserves are widely recognized, community level shifts due to marine reserves have only recently been documented. Protection from fishing of top predators may lead to trophic cascades, which have community-wide implications. Disease may act in a similar manner, regulating population levels of dominant species within a community. Two decades of data from the Channel Islands National Park Service¹s Kelp Forest Monitoring database allowed us to compare the effects of fishing and urchin disease on rocky reef community patterns and dynamics. Different size-frequency distributions of urchins inside and outside of reserves indicated reduced predation on urchins at sites where fishing removes urchin predators. Rocky reefs inside reserves were more likely to support kelp forests than were fished areas. We suggest that this results from cascading effects of the fishery on urchin predators outside the reserves, which releases herbivores (urchins) from predation. After periods of prevalent urchin disease, the reef community shifted more towards kelp forest assemblages. Specific groups of algae and invertebrates were associated with kelp forest and barrens communities. The community dynamics leading to transitions between kelp forests and barrens are driven by both fishing and disease; however the fishery effect was of greater magnitude. This study further confirms the importance of marine reserves not only for fisheries conservation, but also for the conservation of historically dominant community types. Erratum KEY WORDS: Marine reserves · Kelp forest · Urchin barrens · Disease · Rocky reefs · Community description · Discriminant analysis Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 279. Online publication date: September 28, 2004 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2004 Inter-Research.

The biosemiotic complexity of acoustic communities in the primary forests of Ulu Temburong (Brunei, Borneo) and Yasuni (Ecuador, Amazon) was investigated with continuous 24-h recordings, using the acoustic signature and multiscale approach of ecoacoustic events and their emergent fractal dimensions. The 3D recordings used for the analysis were collected in undisturbed primary equatorial forests under the scope of the project, Fragments of Extinction, which produces 3D sound portraits with the highest definition possible using current technologies – a perfect dataset on which to perform a multiscale qualitative analysis. The ecoacoustic events (EEs) detected by a combination of the Acoustic Complexity Indices, ACIft, ACIft evenness, and ACItf evenness, and its fractal dimension were developed according to a biosemiotics approach in which the ecofield theory states that EE functions like a species-specific carrier of meaning. EEs, extracted according to 10 levels of temporal resolution, from 1 to 360 s, confirm the hypothesis that these acoustic communities have an internal complexity that responds to a fractal structure (fractal dimension D of Ulu Temburong D = 1.33 versus Yasuni D = 1.31). Yasuni was richer in EEs, with a higher coefficient of variation of hourly fractal dimension (Yasuni: D = 6.16 versus Ulu Temburong: D = 2.66). This methodology opens up promising new perspectives in the acoustic assessment of habitat quality and monitoring landscape modification. It also confirms the great potential of the biosemiotics approach in converting acoustic frequencies into ecoacoustic events through encoding procedures that mimic potential species-specific interpretations of the sonic environment.

Kelp forest communities are highly variable over space and time. Despite this complexity it has been suggested that kelp forest communities can be classified into one of 2 states: kelp dominated or sea urchin dominated. It has been further hypothesized that these represent "alternate stable states" because a site can remain in either of these states for decades before some perturbation causes a rapid shift to the other state. Our research group has maintained a subtidal community monitoring program for 38 years at San Nicolas Island consisting of twice-annual scuba-based surveys at 6 sites distributed within 4 regions around the island. Three types of perturbations are thought to be relevant to subtidal community dynamics at San Nicolas: (1) physical disturbances in the form of major storm and El Niño/ Southern Oscillation (ENSO) events; (2) invertebrate diseases, which periodically decimate urchin populations; and (3) the reintroduction and subsequent increase of sea otters (Enhydra lutris nereis). These 3 perturbations differ in spatial and temporal specificity; physical disturbances and disease outbreaks occur periodically and could affect all 4 regions, while sea otter predation has been concentrated primarily at the West End sites over the last 15 years. The different types of perturbations and the duration of the time series at the kelp forests at San Nicolas make the data set ideal for testing the "alternate stable state" hypothesis. We use nonmetric multidimensional scaling (NMDS) to examine spatial and temporal patterns of community similarity at the 4 regions. In particular, we evaluate support for the existence of stable states, which are represented on NMDS plots as distinct spatial clusters. Community dynamics at each site approximated a biased random walk in NMDS space, with one or more basins of attraction and occasional jumps between basins. We found evidence for alternative stable states at some sites, and we show that transitions from one stable state to another may be influenced by interactions between multiple perturbations.

Climate change is restructuring ecological communities globally, yet the impacts are often underestimated or poorly resolved due to the lack of historical baselines. In temperate oceans, biologically diverse and socioeconomically important kelp forests are the marine ecosystem most threatened by climate change. However, long-term historical baselines for kelp forests are lacking and the processes driving community-level changes remain poorly resolved. Here, using recently discovered aerial imagery and subtidal quadrat data from 1972, we recreated historical baselines for kelps and associated benthic macroalgae in a global hotspot within the northern Salish Sea (British Columbia, Canada). We resurveyed the same sites in 2023 to quantify community shifts, showing that a half-century ago, bull kelp (Nereocystis luetkeana) formed expansive kelp forests in the region (>550 ha), none of which remain today. Satellite time series of bull kelp show that the majority was lost between 1972 and 1984. These data increase baselines of bull kelp canopy extent in this area by more than 10-fold. Changes to the benthic kelp forest assemblage were mainly driven by loss of the dominant kelp, Saccharina latissima (-78%), across all depths. Historically abundant species of red algae also decreased substantially (e.g., Mazzaella splendens [-98.5%] and Plocamium pacificum, [-62.1%]), largely above three meters depth. Applying the community temperature index (CTI) to this half-century comparison, we show that CTI of the kelp forest community (+1.4°C; 95% CI: 0.43-2.37°C) had tracked increases of summer SST (+1.66°C; 95% CI: 1.20-2.13°C) more closely than winter SST (+0.65°C; 95% CI: 0.46-0.84°C), indicating that temperatures during the hottest summer months are likely driving community shifts. The abundance of cold-affinity species decreased more than warm-affinity species abundance had increased, indicating that the subtidal kelp forest community was predominantly restructured by deborealization, rather than tropicalization. Community deborealization may be prevalent in temperate hotspots that are disjunct from areas with similar climatology, creating colonization barriers for warm-affinity species. Our study underscores the importance of historical data for understanding the true magnitude of climate change impacts and suggests that deborealization of temperate kelp forest communities may be more common than has previously been recognized.

Climatic variables such as temperature and precipitation play an important role in controlling local and regional scale differences in population dynamics and species distributions, and large‐scale climatic events such as El Niño southern oscillation (ENSO) have been shown to affect population dynamics of key species in many ecosystems, particularly in kelp forests. Few studies have been able to evaluate the consequences of climate variables on the structure and dynamics of biological communities, in large part because the lack of data at appropriate spatial and temporal scales has made it difficult to adequately address local‐scale responses of species and communities to such events over relevant time scales. Here, we combined an unprecedented dataset of kelp forest species' abundances from the Channel Islands, California with data for several local, regional, and global scale climatic variables to evaluate the temporal and spatial scale at which one can detect community‐wide effects of climate variables, in particular ENSO events. We found large and significant local‐scale differences in community structure, but these differences were not related to differences in climatic variables. Moreover, giant kelp abundance, which has been shown to be highly sensitive to water temperature and storm disturbance, was a poor predictor of community differences, and all communities tended to decline in abundance over the 20‐year sampling period, suggesting a press perturbation to the system such as PDO cycles or sustained fishing pressure. Although ENSO events can have dramatic impacts on the abundance and distribution of giant kelp itself across the range of the species, such events appear to have little effect on local‐scale kelp forest community structure or dynamics.

Time-series forecasting offers novel quantitative measure to assess loud sound event in an urban park with restored prairie

Kelp forests provide important ecosystem services, yet coastal kelp communities are increasingly altered by anthropogenic impacts. Kelp forests in remote, offshore locations may provide an informative contrast due to reduced impacts from local stressors. We tested the hypothesis that shallow kelp assemblages (12–15 m depth) and associated fish and benthic communities in the coastal southwest Gulf of Maine (GOM) differed significantly from sites on Cashes Ledge, 145 km offshore by sampling five coastal and three offshore sites at 43.0 +/- 0.07° N latitude. Offshore sites on Cashes Ledge supported the greatest density (47.8 plants m2) and standing crop biomass (5.5 kg m2 fresh weight) of the foundation species Saccharina latissima kelp at this depth in the Western North Atlantic. Offshore densities of S. latissima were over 150 times greater than at coastal sites, with similar but lower magnitude trends for congeneric S. digitata. Despite these differences, S. latissima underwent a significant 36.2% decrease between 1987 and 2015 on Cashes Ledge, concurrent with a rapid warming of the GOM and invasion by the kelp-encrusting bryozoan Membranipora membranacea. In contrast to kelp, the invasive red alga Dasysiphonia japonica was significantly more abundant at coastal sites, suggesting light or dispersal limitation offshore. Spatial differences in fish abundance mirrored those of kelp, as the average biomass of all fish on Cashes Ledge was 305 times greater than at the coastal sites. Remote video censuses of cod (Gadus morhua), cunner (Tautaogolabrus adspersus), and pollock (Pollachius virens) corroborated these findings. Understory benthic communities also differed between regions, with greater abundance of sessile invertebrates offshore. Populations of kelp-consuming sea urchins Stronglyocentrotus droebachiensis, were virtually absent from Cashes Ledge while small urchins were abundant onshore, suggesting recruitment limitation offshore. Despite widespread warming of the GOM since 1987, extraordinary spatial differences in the abundance of primary producers (kelp), consumers (cod) and benthic communities between coastal and offshore sites have persisted. The shallow kelp forest communities offshore on Cashes Ledge represent an oasis of unusually high kelp and fish abundance in the region, and as such, comprise a persistent abundance hotspot that is functionally significant for sustained biological productivity of offshore regions of the Gulf of Maine.

Summary A part of biodiversity assessment and monitoring consists in the estimation and track of the changes in species composition and abundance of animal communities. Such a task requires an important sampling over a broad‐scale time that is difficult to reach with classical survey methods. Acoustics may offer an alternative to usual techniques by recording the sound produced by vocal animals. Animal species that use sound for communication (sing and/or call) establish an acoustic community when they sing at the same time and at a particular place. The estimation of the acoustic community dynamics could provide indirect cues on what drives changes in community composition and species abundance. Here, new methods were developed to estimate the changes in bird communities recorded at three woodland temperate sites in France. Both field recordings and simulated data were used to test whether acoustic dissimilarity indices can be used to estimate changes in the composition of the community. Four dissimilarity indices found in the literature, and a new one named Dcf were tested on auditory spectra after transformation to the Mel scale, rather than on classical Fourier frequency spectra. All indices were compared with each other and with compositional indices. The results show that bird communities occurring at the three sites were dynamic with changes of composition with time. Dissimilarities computed on simulated acoustic communities were correlated with compositional dissimilarity but those computed on field‐recorded communities could not be considered as faithful estimators of community composition variations. However, the indices indicate important dates in community changes around mid‐April that were also seen in the composition dynamics. Acoustic dissimilarity indices failed to track accurately changes in species composition of the bird communities. However, these indices, which are easy to compute, still provide information on the acoustic dynamics of bird community. Acoustics might not be considered as a proxy of compositional diversity but rather as another facet of animal diversity that needs to be studied and preserved on its own.

The diversity of animal acoustic signals has evolved due to multiple ecological processes, both biotic and abiotic. At the level of communities of signaling animals, these processes may lead to diverse outcomes, including partitioning of acoustic signals along multiple axes (divergent signal parameters, signaling locations, and timing). Acoustic data provides information on the organization, diversity and dynamics of an acoustic community, and thus enables study of ecological change and turnover in a non-intrusive way. In this review, we lay out how community bioacoustics (the study of acoustic community structure and dynamics), has value in ecological monitoring and conservation of diverse landscapes and taxa. First, we review the concepts of signal space, signal partitioning and their effects on the structure of acoustic communities. Next, we highlight how spatiotemporal ecological change is reflected in acoustic community structure, and the potential this presents in monitoring and conservation. As passive acoustic monitoring gains popularity worldwide, we propose that the analytical framework of community bioacoustics has promise in studying the response of entire suites of species (from insects to large whales) to rapid anthropogenic change.

Foundation species have strong, positive effects on local community structure; increasing biodiversity and species abundances by providing food and habitat. On coastal temperate and subpolar rocky reefs, canopy-forming kelps form three-dimensional habitats that support numerous fish, invertebrate, and algal species. Throughout the Aleutian Archipelago, unregulated sea urchin grazing has largely removed the foundation canopy-forming kelp, Eualaria fistulosa, and most subcanopy algae. Consequently, most nearshore rocky reefs have shifted from kelp to sea urchin (Strongylocentrotus spp.) dominated habitats. These latter habitats are either urchin barrens devoid of all fleshy macroalgae, or transition forests devoid of all fleshy macroalgae algae but E. fistulosa. These three distinct communities (kelp and transition forests, and urchin barrens) were used to test the influence of E. fistulosa and sea urchins on the associated communities. Contrary to initial expectations, in transition forest habitats where E. fistulosa is the lone macroalga, no differences in community structure or in the size structure of benthic invertebrates were seen relative to urchin barrens. In kelp forests, where E. fistulosa coexisted with subcanopy macroalgae and urchins were less abundant, faunal communities were more species rich with higher abundance, biomass, and percent cover of numerous filter feeders. These findings stress not only the strong negative impact which urchins can exert on the kelp forest communities, but also the context-dependent nature of foundation species.

New Caledonia is a Pacific island with a unique biodiversity showing an extreme microendemism. Many species distributions observed on this island are extremely restricted, localized to mountains or rivers making biodiversity evaluation and conservation a difficult task. A rapid biodiversity assessment method based on acoustics was recently proposed. This method could help to document the unique spatial structure observed in New Caledonia. Here, this method was applied in an attempt to reveal differences among three mountain sites (Mandjélia, Koghis and Aoupinié) with similar ecological features and species richness level, but with high beta diversity according to different microendemic assemblages. In each site, several local acoustic communities were sampled with audio recorders. An automatic acoustic sampling was run on these three sites for a period of 82 successive days. Acoustic properties of animal communities were analysed without any species identification. A frequency spectral complexity index (NP) was used as an estimate of the level of acoustic activity and a frequency spectral dissimilarity index (Df) assessed acoustic differences between pairs of recordings. As expected, the index NP did not reveal significant differences in the acoustic activity level between the three sites. However, the acoustic variability estimated by the index Df, could first be explained by changes in the acoustic communities along the 24-hour cycle and second by acoustic dissimilarities between the three sites. The results support the hypothesis that global acoustic analyses can detect acoustic differences between sites with similar species richness and similar ecological context, but with different species assemblages. This study also demonstrates that global acoustic methods applied at broad spatial and temporal scales could help to assess local biodiversity in the challenging context of microendemism. The method could be deployed over large areas, and could help to compare different sites and determine conservation priorities.