Episodic reductions in underwater light can be a key driver of marine ecosystem degradation. Yet a consistent event-based framework describing the frequency, duration and intensity of substantial but short-term reductions in underwater light does not exist. Here, we proposed marine darkwaves as a framework for quantifying these episodic reductions of underwater light at specific depths which aligns with definitions of other episodic and extreme events. The framework was applied to long-term in situ time series of underwater irradiance from California, USA (16 years, 6.3 metres) and New Zealand (10 years, at 7 and 20 metres). We showed evidence of several intense marine darkwaves across these sites, with durations up to 64 days, cumulative light deficits reaching −105.6 mol photon·m−2, and up to almost 100

Abstract Numerous stressors are driving long‐term declines in coral cover on coral reefs, significantly impacting reef fish biodiversity and community structure. The benthic space made available by declining coral cover is often occupied by increases in other organisms, including macroalgae, encrusting ascidians, and sponges. Using a combined observational and experimental approach, we examined whether encrusting sponges impact fish communities as they replace corals on degraded reefs. First, fish assemblages were compared across 36 quadrats (3 × 3 m) with sponge cover ranging from 0% to 60%, primarily comprised of the species Lamellodysidea cf. chlorea and Lamellodysidea sp. Second, we quantified fish responses to the experimental removal of sponges from 12 additional quadrats with high sponge cover (>20%). High sponge cover (>20%) was associated with a significant reduction in fish abundance (39% fewer individuals) and species richness (26% fewer species) compared to areas with lower sponge coverage. While these differences showed some correlation with reduced substratum complexity, they were independent of coral cover and depth. Distinct fish communities were associated with high and low sponge coverage. High‐sponge areas were dominated by larger species, such as the surgeonfish Ctenochaetus tominiensis, damselfishes Neoglyphidodon nigroris and Amblyglyphidodon leucogaster, and snapper Lutjanus biguttatus. In contrast, areas with less than 20% sponge cover primarily hosted smaller cryptobenthic and coral‐associated fish species. Interestingly, experimental sponge removal did not affect overall fish abundance or species richness after 100 days, as both removal and control sites showed similar temporal increases. However, significant differences in fish community composition emerged within just 7 days post‐removal. High‐sponge areas retained distinct assemblages, containing 42 exclusive species (38% of total), including characteristic residents like Ctenochaetus binotatus, N. nigroris, and L. biguttatus. Conversely, sponge removal zones attracted 18 unique species (21%), predominantly generalist and rubble‐associated fishes such as Pomacentrus aurifrons and Apogon neotes, revealing rapid but transient shifts in community structure following habitat modification. These results indicate that encrusting sponges exert a substantial influence on local fish assemblages. The differences between the observational and experimental results likely reflect both long‐term and short‐term effects of encrusting sponges on coral reef fish communities.

River mouths are important indicators and mediators of interactions between rivers and the sea that mark the dispersal point for catchment-based stressors and subsidies. Satellite remote sensing data products and algorithms present many new possibilities for monitoring these dynamic and often inaccessible environments. In this study, we describe a national-scale comparative framework based on proximity to river mouths and show its application to the monitoring of coastal ecosystem health in Aotearoa New Zealand. We present results from light attenuation coefficient (Kd) analyses used to develop the framework considering data products of differing resolution and the effects of coastline geometries which might obscure the influence of catchment-derived stressors. Ten-year (2013–2022) Kd values from the highest-resolution product (500 m) showed significant differences (p < 0.01) in successively larger radii (1–20 km) despite the confounding influence of adjacent river mouths. Smaller radii returned a high variability that dropped markedly > 5 km. Tests of a 10 km radius showed that coastline geometry had a significant influence on Kd (p < 0.001), which is also likely for other water quality indicators. An analytical approach stratified by coastline geometry showed significant effects of stream order on open (p < 0.01) but not enclosed coasts, differences between marine bioregions (p < 0.05), and a degradation trend in the 90th percentile of Kd on enclosed coasts, which is indicative of extreme events associated with catchment erosion or sediment resuspension. We highlight applications of the framework to explore trends across many other meaningful scales (e.g., jurisdictions and ecosystem types) in addition to tracking changes at individual river mouths.

The biogeography of marine benthic assemblages worldwide is shifting to higher latitudes in response to climate change. Concurrently, extreme weather events are exacerbating environmental stressors. As is typical globally for temperate regions, sponge communities dominate the mesophotic reefs of the Motiti archipelago in the Bay of Plenty (east coast, North Island New Zealand). Although recently classified as a marine reserve for its importance as a refuge for fish and targeted invertebrates (crayfish, abalone/pāua, and sea urchins), the benthos was largely unexplored prior to this research. A series of recent cyclonically associated sedimentation and concurrent marine heatwave events provided an opportunity to examine responses of this benthic-pelagic assemblage important in trophic connectivity. Biogeographic affinities of Motiti’s mesophotic reef benthos were established using remotely operated vehicles (ROVs). Fifty-three sponge species were conservatively identified: 22% representing the southernmost (highest latitude) geographic range recorded to date. Simultaneously, this community may be under threat by the changing marine climate that supported its establishment. Widespread sponge tissue necrosis (especially of Choristid sponges) and sediment smothering of encrusting benthos coincided with the sudden decline of a ‘tumbleweed sponge’ (species unknown). These observations co-occurred with a marine heat wave and major cyclonic event delivering fine sediments to these offshore reefs. This research provides a more nuanced understanding of short- and possibly long-term effects of multiple stressors on mesophotic benthic ecosystems. This newly identified biodiversity hotspot supporting southernmost ranges of Australasian species and its seemingly rapid deterioration, signals a warning for the stability of temperate mesophotic ecosystems.

Sponge assemblages are becoming increasingly important in structuring coral reef systems. Encrusting sponges frequently establish and interact with corals competing over space. Sponge-coral competitive interactions are dynamic and can reshape coral reef systems. We evaluated interactions between sponges and corals by (1) documenting the percent cover and occurrence of encrusting sponges on dead and live corals of different morphologies at 5 and 10 m depth; (2) recording the outcome of 85 sponge-coral interactions for a 138 day period; and (3) transplanting fragments of two common sponge species Dysidea sp. 1 and Lamellodysidea cf., chlorea, to assess their ability to attach and grow on dead and live corals of branching and massive morphologies. Sponges occurred more frequently on dead coral skeletons of encrusting, branching, massive and foliose morphologies with Dysidea sp. 1 and L. cf., chlorea accounting for 50% of all sponges observed. Sponge prevalence on live corals doubled from 5 to 10 m depth. Natural sponge-coral interactions indicated both overgrowth and retreat of sponges, with few apparent stand-offs. Dysidea sp. 1 and L. cf., chlorea overgrew corals in 39 and 77% of the natural interactions respectively. Approximately half of the sponge transplants attached to corals and 47% showed evidence of growth. Sponge occupation appeared to vary between sponge species and to be associated with coral condition, coral morphology, and depth.

A practical two-product cascading biorefinery was developed to extract a biostimulant and cellulose from the freshwater filamentous macroalga Oedogonium calcareum grown while treating primary wastewater. Biostimulant production provides a valuable extract with production of disinfected residual biomass for further product development. Both Escherichia coli and F-specific RNA bacteriophage, indicators of human pathogens contamination, were absent from the residual biomass. The chemical composition of the biostimulant was complex, consisting of growth-promoting substances, free amino acids, and minerals. The O. calcareum cellulose fractions yielded between 9.5% and 10.1% (w/w) with purities from 84% to 90% and closely resembled microcrystalline cellulose. Biostimulant extraction improved cellulose quality by increasing crystallinity from 59% to 62%. Biomass condition, drying process, and biostimulant production influenced the crystallinity index. This study demonstrates a two-step process of biostimulant and cellulose extraction from wastewater-grown Oedogonium, simultaneously disinfecting biomass and isolating high-quality cellulose as a sustainable alternative to conventional extraction methods.

Five new sulfated arylpyrrole and arylpyrrolone alkaloids, denigrins H–L (1–5), along with two known compounds, dictyodendrin B and denigrin G, were isolated from an extract of a New Zealand Dictyodendrilla c.f. dendyi marine sponge. Denigrins H–L represent the first examples of sulfated denigrins, with denigrins H and I (1–2), as derivatives of denigrin D, containing a pyrrolone core, and denigrins J–L (3–5), as derivatives of denigrin E (6), containing a pyrrole core. Their structures were elucidated by interpretation of 1D and 2D NMR spectroscopic data, ESI, and HR-ESI-MS spectrometric data, as well as comparison with literature data. Compounds 1–5, along with six known compounds previously isolated from the same extract, showed minimal cytotoxicity against the HeLa cervical cancer cell line.

In New Zealand, during the hottest periods of the year, some salmon farms in the Marlborough Sounds reach water temperatures above the optimal range for Chinook salmon. High levels of mortality are recorded during these periods, emphasising the importance of understanding thermal stress in this species. In this study, the responses of Chinook salmon (Oncorhynchus tshawytscha) to chronic, long-term changes in temperature and dissolved oxygen were investigated. This is a unique investigation due to the duration of the stress events the fish were exposed to. Health and haematological parameters were analysed alongside gene expression results to determine the effects of thermal stress on Chinook salmon. Six copies of heat shock protein 90 (HSP90) were discovered and characterised: HSP90AA1.1a, HSP90AA1.2a, HSP90AA1.1b, HSP90AA1.2b, HSP90AB1a and HSP90AB1b, as well as two copies of SOD1, named SOD1a and SOD1b. The amino acid sequences contained features similar to those found in other vertebrate HSP90 and SOD1 sequences, and the phylogenetic tree and synteny analysis provided conclusive evidence of their relationship to other vertebrate HSP90 and SOD1 genes. Primers were designed for qPCR to enable the expression of all copies of HSP90 and SOD1 to be analysed. The expression studies showed that HSP90 and SOD1 were downregulated in the liver and spleen in response to longer term exposure to high temperatures and lower dissolved oxygen. HSP90 was also downregulated in the gill; however, the results for SOD1 expression in the gill were not conclusive. This study provides important insights into the physiological and genetic responses of Chinook salmon to temperature and oxygen stress, which are critical for developing sustainable fish aquaculture in an era of changing global climates.

Substratum preferences and contact interactions among sessile organisms can be a major determinant of biotic gradients in the structure of benthic communities on coral reefs. Sponges are a substantial component of these communities, but their substratum requirements and interactions with other benthic taxa are poorly understood. Here, we quantified sponge substratum preferences and interactions from 838 randomly selected photo-quadrats across different depths (5, 10 and 15 m), exposure (sheltered and exposed), and substratum topography (horizontal, inclined and vertical surfaces) on coastal coral reefs in Kimbe Bay. A high proportion (55%) of sponge colonies were associated with dead coral, unconsolidated coral rubble (7%) and calcium carbonate rock (CaCO 3 rock) (7%), even though they represented only 10%, 4% and 1% of the available substratum, respectively. Sponges interacted most frequently with algae (~ 34%), corals (~ 30%) and crustose coralline algae (CCA ~ 19%) that represented ~ 46%, ~ 18% and ~ 14% of the substratum cover, respectively. The microhabitat preferences of sponges and frequency of interactions with other taxa were mostly consistent across various exposure, depth and substratum topography conditions. Most interactions appeared to be “stand-offs” (71%) which are interactions with no clear winner or loser. However, when overgrowth occurred, sponges were usually winners, overgrowing corals (92%), CCA (81%) and macroalgae (65%). Three sponge species Dysidea sp1, Lamellodysidea cf. chlorea and Lamellodysidea chlorea accounted for 51% to 96% of the overgrowth of sponges over algae, corals and CCA, but there was no one species found to always win or lose. Our results suggest that sponges avoid other biological substrata by preferentially settling on dead coral, coral rubble and CaCO 3 rock, but when they do come into contact with algae and corals, they frequently overgrow their spacial competitors.

Feeding-choice experiments were conducted under laboratory conditions with two dorid spongivorous nudibranchs, Goniobranchus aureomarginatus and Ceratosoma amoenum, collected from a sponge meadow off Tauranga, New Zealand with two sponge prey (Dysidea teawanui sp.nov. and an undescribed species from the Dictyodendrillidae family, possibly Dictyodendrilla tenella (Lendenfeld 1888). The first choice of prey, the total number of prey choices made, and the time spent on each prey target was recorded, results indicating that each nudibranch had strong preferences for specific prey species. Preferences were significant when the time spent grazing on prey was taken into consideration. Goniobranchus aureomarginatus had a strong preference for the undescribed Dictyodendrillid sponge, while Ceratosoma ameonum preferred Dysidea teawanui. The results of the feeding-choice experiments matched observations in the wild. Chemical analysis of the undescribed Dictyodendrillid sponge led to the isolation and characterisation of six known bioactive metabolites, dictyodendrin C (1), D (2) and F (3), as well as denigrin E (4), dactylpyrrole A (5) and lamellarin O1 (6). Two of the known compounds, dictyodendrins C (1) and F (3) were also isolated from G. aureomarginatus individuals. Chemical analysis of D. teawanui afforded ergosterol peroxide, 5α,8α-epidioxy-24-methylcholesta-6,22-dien-3β-ol (7). The structures of the isolated natural products were elucidated based on extensive analysis of 1D and 2D NMR data.

Coral reef benthic communities include a wide range of taxa, but most attention has been given to hard coral assemblages, and how their cover and composition vary over strong spatial gradients. Much less is known about the spatial distribution and composition of coral reef sponge communities, which may become increasingly important on reefs with declining coral cover. Here, we examined the effects of exposure, depth, aspect and location on the cover and composition of sponge assemblages on a coral reef in Kimbe Bay, Papua New Guinea. We quantified sponge cover and species composition along replicate line transects on 6 inshore reefs, sampling exposed (seaward) and sheltered (landward) sides of reefs at 5, 10 and 15 m depth, with reef aspect subdivided into slopes or walls along each transect. Although the substratum was generally dominated by corals and algae, sponges ranked 3rd, with an average of 13.1% cover, including 63 recognisable species. Morphologically there were 38 encrusting, 21 erect and 4 massive sponge species, with the encrusting sponges Lamellodysidea cf. chlorea and Dysidea sp1 exhibiting the highest cover. Sponge cover, species richness and species composition all exhibited complex interactions among depth, exposure and location. Sponge cover and species richness increased in transects with higher percentages of wall aspects, and assemblage structure differed between slopes and walls. Sponges are a diverse component of the benthos, with exposure, depth and reef aspect all contributing to explain spatial variation in assemblage structure.

Sponges (Porifera) are a key component of many coral reef ecosystems. In some biogeographic regions, they are considered the dominant benthic fauna and they have the capacity to fulfil many similar roles to reef-building scleractinians. Certainly, sponges predominate at depth, below the critical thresholds of most coral species. The biological and physical attributes of these biogenic communities contribute essential resources for many reef-associated fishes. However, while fish–sponge interactions have been widely documented, there is no global synthesis of the literature on these interrelationships from the perspective of fish ecology. Here we evaluate coral reef fish–sponge relationships, including the role of sponges in providing food and shelter for fishes, the influence fishes have on sponge distribution and abundance and possible outcomes of climate change on fish–sponge interactions. To date, 16 fish families have been shown to associate with 56 different sponge genera, using them as either a source of shelter (n = 17) or a food source (n = 50), although methodologies for the latter currently lack consistency. We demonstrate that a more comprehensive understanding of fish–sponge interactions has been garnered from tropical Atlantic coral reefs, which has resulted in a strong biogeographic bias. While it is evident that in some areas of the Caribbean fish are key in shaping the distribution and abundance of sponges, it is not yet known whether this conclusion applies to the Indo-Pacific. With increasing stresses such as bleaching events impacting coral reef ecosystems, further work is needed to evaluate whether sponges can fulfil similar functional roles to those previously provided by reef-building scleractinians. Similarly, determining whether sponge expansion will compensate for the negative effects of reef degradation, or contribute to their decline, is vital.

Differentiation of species within the genus Dysidea Johnston, 1842 (Order Dictyoceratida Minchin, 1900, Family Dysideidae Gray, 1867) is extremely difficult as they lack spicules which are strongly diagnostic in other Demospongiae, and their primary and secondary fibres and the mesh that they form, may be irregular in shape and thickness, thus difficult to measure for comparisons. Here we review species of Dysidea known from the New Zealand Exclusive Economic Zone (EEZ), validating five species: Dysidea cristagalli Bergquist, 1961a, from the Hauraki Gulf; D. hirciniformis (Carter, 1885a) sensu Dendy (1924), from North Cape; D. navicularis Lendenfeld, 1888, from Port Lyttleton on the east coast of the South Island; D. ramsayi (Lendenfeld, 1888) from the Chatham Islands; D. spiculivora Dendy, 1924, from Cape Maria Van Diemen and the Three Kings Islands to the north of New Zealand. Dysidea fragilis (Montagu, 1818) sensu Bergquist (1961b), from Mernoo Bank on Chatham Rise, is now considered to be invalid, and D. elegans (Nardo, 1847) sensu Brøndsted (1927), from the Coromandel Peninsula, is considered unrecognisable. Several partially characterised species have also been cited in the literature. Two new species from Tauranga Harbour, on the northeast coast of the North Island, Dysidea tuapokere sp. nov. and D. teawanui sp. nov., are described. These descriptions are based on fresh material and in situ photography, facilitating clear, informative descriptions, that will enable ease of identification of these species in the future.

Coarse-grained hard substrate areas with grain sizes up to very coarse boulder (> 2 m) are very rare in the German North Sea. The “Helgoländer Steingrund” is one of such highly biodiverse areas: it is characterized by a half-moon-shaped hard substrate ridge, which subdivides the site into a more exposed (westerly) and a less exposed (easterly) flank, characterized by a mixture of sand and gravel deposits. Sonar systems, underwater videos, and bottom samples were used for mapping and classifying the abiotic and biotic components in such very patchy and coarse-grained habitat. Three main seabed types (sand, gravel, and hard substrate) were identified, based on acoustic backscatter data. The additional information coming from underwater videos and sediment bottom sample analysis allowed the description of six different seabed types, which included both the abiotic (sediments, morphology, etc.) and biotic components. The flanks of the ridge and their transition to the surrounding soft-ground areas were characterized by a distinct dominance of the bryozoa F. foliacea and A. diaphanum on the western and on the eastern side, respectively. Morphology and hydrodynamics are likely responsible for such zonation. This is proved by the outcomes of the Acoustic Doppler Current Profiler data, which showed the general flow pattern across the ridge and even resolved the local variability of current pattern, dependent on the tidal stage and bottom relief.

Scleractinian corals, primarily plate corals in families Agaricidae and Acroporidae, were monitored in situ before, during and after a 3D marine seismic survey. An initial four day seismic run, resulting in a maximum 24 h received sound exposure level (SEL24) of 204 dB re 1 μPa2·s and received 0-to-peak pressure (PK Pressure) of 226 dB re 1 μPa, had no detectable effect on soft tissues or skeletal integrity. Subsequently, a full marine seismic survey (Maxima 3D MSS), proceeded over two months and included seismic acquisition lines at 240 m spacing over the broader reef lagoon (South Scott Reef), generating maximum received SEL24 of 197 dB re 1 μPa2·s and received PK Pressure of 220 dB re 1 μPa at the coral monitoring sites. The analysis detected no effect of seismic activity measured as coral mortality, skeletal damage or visible signs of stress immediately after and up to four months following the 3D marine seismic survey.

Marine reserves exhibit increases in targeted fish species, but long-term effects on biodiversity are poorly understood. Factors other than reserve status may affect decadal changes, including environmental change. We examined the fish fauna at the iconic Poor Knights Islands over 4 decades (1974–2016) before and after implementation of a no-take marine reserve in 1998. We document a substantial increase in commercially and recreationally targeted Chrysophrys auratus, which was virtually absent before 1994 but by 2016 had reached up to 11 fish per 500m2 (220 per hectare). There were also large changes to the fish community, including the decline of subtropical and coastal wrasses, some species with no change and others that increased significantly. Many declines occurred >20 years before the arrival of abundant C. auratus, suggesting the changes do not represent a trophic cascade. Furthermore, this normally benthic-feeding fish has adopted a mid-water foraging behaviour targeting planktivorous fish. The increase in C. auratus appears to be linked both to reserve status and catch regulations in the wider region. Overall, the data point to long-term environmental fluctuations from the late 1970s having a negative effect on the abundance of more than half the reef fish species at these islands.

Overland transport in open-air-exposed conditions, including the translocation of specimens fouled on trailered boat hulls, aquaculture ropes or entangled in fishing gear, is recognized as a short-distance vector for the introduction of invasive aquatic species. Here, the desiccation tolerance for different life stages of the invasive kelp Undaria pinnatifida was determined to test the likelihood of air-exposed transport. Water content, photosynthetic quantum yield (Fv/Fm) as well as the capacity to release viable spores were monitored for mature sporophylls during a five-day exposure to air conditions. For newly settled spores (16h post-release) and developing gametophytes (30h post-release) survival and growth were observed after 1, 3, 6, 12 and 24h of desiccation. Additionally, spore settlement and desiccation survival (after 3, 12 and 48h) were determined for seven-day-old gametophytes growing on different rope materials (hemp, polypropylene, polyethylene, nylon) in high (99% relative air humidity, RH) and typical (59% RH) air humidity conditions. Viable spores were released from mature sporophylls after three days of desiccation. <0.4% of spores and gametophytes survived air exposure. Of those surviving, however, individual gametophytes could endure 12h of desiccation. These specimens exhibited enhanced average lengths, growing up to 70% larger than control gametophytes. Attached to ropes, gametophytes survived 48h of desiccation; settlement and desiccation survival did not differ between rope materials. Overall, this study demonstrates that air-exposed transport, especially the translocation of mature sporophylls, represents a potential spread mechanism for the invasive U. pinnatifida. This is a vector that should be considered for pest management.

Magnetic susceptibility and electric conductivity within the uppermost meter of the seafloor were measured with high resolution along 33 coast-normal profiles in the Bay of Plenty (New Zealand), using the recently developed electromagnetic benthic profiler MARUM NERIDIS III. These parameters are used to determine magnetic mineral concentration and porosity of mostly volcanoclastic sediments between 2 and 35m water depth to investigate distribution and formation of magnetic mineral enrichments on a storm-dominated shelf.In general, magnetic mineral concentration (susceptibility) is inversely correlated to porosity (conductivity). Along profiles, susceptibility maxima and conductivity minima were commonly found on bathymetrical elevations such as dune and ripple crests. Cores and grab samples show the highest degree of enrichment in the uppermost 20cm of the seafloor. Complementing petromagnetic analysis indicates a spectrum of FeTi-oxides in the sediment, ranging from magnetite and hematite over titanomagnetite (TM40 and TM60) to titanohematite (likely TH80 and TH95).Three distinct zones of magnetic mineral enrichment could be identified: a coast-parallel structure with low porosity in recent fine sand between 5 and 20m water depth, a widespread structure with low porosity in older, transgressionally reworked, coarse sand in up to 30m water depth, and third structure coarse sand with high porosity located mostly below 30m. While the fine sand structure is interpreted as the result of an active process, the other two appear to be relics. Sorting by grain size selective entrainment appears to be the major formation mechanism.This study demonstrates how electromagnetic benthic profiling, in combination with environmental magnetic laboratory analysis, provides reliable, highly interpretable data that allow insight into sorting processes within the boundaries of established lithofacies that are difficult to detect using a classical sedimentological approach.

To investigate the uptake and depuration of polycyclic aromatic hydrocarbons associated with the Rena oil spill we sampled the surf clam Paphies subtriangulata at two open coast locations (6km apart) just prior to oil coming ashore (7 October 2011), then at 1-3 week intervals for the next 4 months. Total polycyclic aromatic hydrocarbons (tPAH) increased at both sites from 1 to 96-124 mu g kg(-1) (wet weight) by 18 October before declining to low levels (<4 mu g kg(-1)) by February 2012. Ongoing sampling throughout 2012-2014 included three additional sites to the north east (up to 30 km away) and a site 5 km to the south east revealing tPAH levels generally <10 mu g kg(-1) except in October 2013 where levels ranged between 39-45 mu g kg(-1) at all sites. A comparison of PAH component profiles with oil-contaminated beach sediment indicated that the high levels observed in surf clams between October-December 2011 were clearly associated with the Rena spill. However, the October 2013 peak had a PAH profile inconsistent with weathered Rena oil, suggesting an alternative source of contamination. Our results highlight the potential for P. subtriangulata as a PAH monitoring tool but recognise more study is needed to better quantify baseline levels and uptake and depuration dynamics.