Abstract:Foundation species play a disproportionate role in maintaining biodiversity and ecosystem functioning. Improved understanding of how environmental factors influence the distribution and population structure of foundation species therefore contributes to management and conservation of entire ecosystems. We surveyed subtidal kelp forests within four regions of the U.K., distributed over 9 of latitude and a mean sea temperature gradient of $ 2.5 C. Our aims were: (1) to examine relationships between light availab… Show more
“…The overlapping light absorption by water column phytoplankton and both green and brown algae action spectra has implications for light harvesting at the seabed and suggests that eutrophication-induced phytoplankton bloom could substantially affect the structure and functioning of benthic macroalgal assemblages, especially at the extremities of light limitation in coastal scenarios (confirming Hypothesis 3). Changes in light availability in terms of quantity, which is usually integrated over the PAR range (400-700 nm), is well known to significantly affect benthic macroalgae assemblages (Airoldi 2003;Clark et al 2013), resilience (Desmond et al 2015;Tait 2019), and their associated ecosystem services like carbon cycles (Blain et al 2021;Smith et al 2021;Weigel and Pfister 2021). However, benthic light also has a spectral quality component, and it is still unclear how changes in spectral light quality tied to changes in OACs in the water column are related to patterns of occurrence in macroalgal communities.…”
Section: Discussionmentioning
confidence: 99%
“…Most macroalgal assemblages exist in optically complex coastal waters (Gattuso et al 2020; Duarte et al 2022), where a range of land and ocean‐derived organic and inorganic matter alter the absorption and backscatter of light and hence the spectral attenuation of light with depth. It is well known that a shifting light climate has the potential to greatly influence competitive dynamics of macroalgal assemblages with significant implications for net primary productivity, standing biomass, and rates of carbon sequestration (Clark et al 2013; Desmond et al 2015; Tait and Schiel 2018; Tait 2019; Blain et al 2021; Smith et al 2021; Weigel and Pfister 2021). For example, some coastal zones of New Zealand (NZ) experience high levels of sediment runoff (Schiel and Howard‐Williams 2016), and these are associated with detrimental impacts to benthic macroalgal communities (Alestra et al 2014; Tait 2019; Blain et al 2020; Tait et al 2021).…”
Compromised light quantity on the seabed affects the composition and resilience of marine forests and the maintenance of ecosystem services. However, the response of macroalgal assemblages to changes in the quality (spectral composition) of light as compared to the quantity alone is poorly understood. Here, we bridge radiative transfer modeling and algal physiology to simulate the underwater light environment and explore macroalgal responses to spectral attenuation by various coastal water constituents. We considered three groups of macroalgal taxa (class Phaeophyceae and, phyla Chlorophyta and Rhodophyta) for which we developed a “synthetic envelope” of spectrally resolved action spectra using 1 million radiative simulations. We found that brown algae were more efficient at harvesting light across the whole spectrum at low attenuation (< 0.2 m−1) when depths were greater than 10 m, whereas green algae dominated shallower depths than 10 m for low to high attenuation values. Finally, red algae made best use of the available light at relatively higher attenuation values (> 0.2 m−1) and deeper depths. We also demonstrated that the brown and green algal taxa showed higher photosynthetic efficiencies when attenuation was dominated by particulate matter rather than by phytoplankton or detrital matter. Our results shed new light on the “Complementary Chromatic Adaptation” hypothesis by confirming that algal pigmentation matters under a subset of scenarios, particularly at the limits of light availability in coastal waters. This study paves the way for identifying competitive thresholds in macroalgal communities by using satellite‐derived ocean color products to identify regions and depths of potential optical transitions.
“…The overlapping light absorption by water column phytoplankton and both green and brown algae action spectra has implications for light harvesting at the seabed and suggests that eutrophication-induced phytoplankton bloom could substantially affect the structure and functioning of benthic macroalgal assemblages, especially at the extremities of light limitation in coastal scenarios (confirming Hypothesis 3). Changes in light availability in terms of quantity, which is usually integrated over the PAR range (400-700 nm), is well known to significantly affect benthic macroalgae assemblages (Airoldi 2003;Clark et al 2013), resilience (Desmond et al 2015;Tait 2019), and their associated ecosystem services like carbon cycles (Blain et al 2021;Smith et al 2021;Weigel and Pfister 2021). However, benthic light also has a spectral quality component, and it is still unclear how changes in spectral light quality tied to changes in OACs in the water column are related to patterns of occurrence in macroalgal communities.…”
Section: Discussionmentioning
confidence: 99%
“…Most macroalgal assemblages exist in optically complex coastal waters (Gattuso et al 2020; Duarte et al 2022), where a range of land and ocean‐derived organic and inorganic matter alter the absorption and backscatter of light and hence the spectral attenuation of light with depth. It is well known that a shifting light climate has the potential to greatly influence competitive dynamics of macroalgal assemblages with significant implications for net primary productivity, standing biomass, and rates of carbon sequestration (Clark et al 2013; Desmond et al 2015; Tait and Schiel 2018; Tait 2019; Blain et al 2021; Smith et al 2021; Weigel and Pfister 2021). For example, some coastal zones of New Zealand (NZ) experience high levels of sediment runoff (Schiel and Howard‐Williams 2016), and these are associated with detrimental impacts to benthic macroalgal communities (Alestra et al 2014; Tait 2019; Blain et al 2020; Tait et al 2021).…”
Compromised light quantity on the seabed affects the composition and resilience of marine forests and the maintenance of ecosystem services. However, the response of macroalgal assemblages to changes in the quality (spectral composition) of light as compared to the quantity alone is poorly understood. Here, we bridge radiative transfer modeling and algal physiology to simulate the underwater light environment and explore macroalgal responses to spectral attenuation by various coastal water constituents. We considered three groups of macroalgal taxa (class Phaeophyceae and, phyla Chlorophyta and Rhodophyta) for which we developed a “synthetic envelope” of spectrally resolved action spectra using 1 million radiative simulations. We found that brown algae were more efficient at harvesting light across the whole spectrum at low attenuation (< 0.2 m−1) when depths were greater than 10 m, whereas green algae dominated shallower depths than 10 m for low to high attenuation values. Finally, red algae made best use of the available light at relatively higher attenuation values (> 0.2 m−1) and deeper depths. We also demonstrated that the brown and green algal taxa showed higher photosynthetic efficiencies when attenuation was dominated by particulate matter rather than by phytoplankton or detrital matter. Our results shed new light on the “Complementary Chromatic Adaptation” hypothesis by confirming that algal pigmentation matters under a subset of scenarios, particularly at the limits of light availability in coastal waters. This study paves the way for identifying competitive thresholds in macroalgal communities by using satellite‐derived ocean color products to identify regions and depths of potential optical transitions.
“…For example, M. brachydactyla individuals undertake long-distance migrations into deeper waters on reaching sexual maturity (Corgos et al, 2006), whilst mass recruitment and mortality events of crabs and lobsters have been associated with extreme environmental conditions (e.g. marine heatwaves, see Smith et al, 2021b), both of which contribute to pronounced temporal variability in crustacean population density and size structure. Moreover, decapod crustaceans often exhibit nocturnal or crepuscular peaks in foraging activity (Ennis, 1984;Davenport et al, 2021) and would have been underrepresented in our daytime sampling.…”
Section: Discussionmentioning
confidence: 99%
“…Nutrients were not measured but the study area within the NE Atlantic is not characterized by major upwelling regimes, and previous snapshot sampling at our study sites and longer time series within the regions shows that nutrient concentrations are comparable across this gradient with no difference in key nutrient concentrations between our study sites (Pessarrodona et al ., 2018; Smale et al ., 2020 b ). Previous work at these study sites has shown that they are characterized by extensive kelp canopies dominated by L. hyperborea (Smale et al ., 2016; Smale & Moore, 2017), which extend from the subtidal fringe to depths of ~20 m (Smith et al ., 2021 a ), and support rich and abundant assemblages of associated invertebrates and macroalgae (Teagle et al ., 2018; Bué et al ., 2020; Smale et al ., 2020 a ; King et al ., 2021). Fig.…”
Kelp forests are regarded as important nursery and foraging habitats for commercially important species of finfish and shellfish despite an absence of fishery-independent data in many regions. Here, we conducted targeted surveys at 12 subtidal reefs, distributed across 9° of latitude in the UK, using three complementary techniques (Underwater Visual Census (UVC), Baited Remote Underwater Video (BRUV) and deployment of prawn pots) to quantify the abundance of crustaceans within kelp forests. Commercially important species were recorded at all sites; Cancer pagurus (brown/edible crab) and Necora puber (velvet swimming crab) were the most abundant and commonly observed, although Maja brachydactyla (spider crab), Homarus gammarus (European lobster) and Palaemon serratus (common prawn) were also recorded. The abundance of some species exhibited pronounced regional variability, with higher abundances of C. pagurus within northern regions and, conversely, higher abundances of M. brachydactyla and P. serratus within southern regions. Each sampling technique yielded similar spatial patterns for the most abundant species but had varying sensitivity to some species. Most individuals observed were juvenile or sub-adults, suggesting kelp forests serve as important nursery grounds for commercially and ecologically important crustaceans. Further monitoring efforts, conducted across greater spatiotemporal scales and in different habitat types, are needed to provide a robust baseline against which to detect changes and to inform management and conservation actions.
“…However, marine forests are shrinking globally 17,18 due to several impacts such as urbanisation, marine farming, local pollution and herbivory 11,19,20 ; making these habitats more sensitive to global change 5,21 . The structure and productivity of marine forests are influenced by many environmental factors that drive the growth, survival, reproduction and metabolism of the organisms, which in turn affect the whole habitat or ecosystem [22][23][24] . Global change effects on marine forests can vary according to the location, the population characteristics and the species 20,25,26 .…”
Marine forests are shrinking globally due to several anthropogenic impacts including climate change. Forest-forming macroalgae, such as Cystoseiras.l. species, can be particularly sensitive to environmental conditions (e.g. temperature increase, pollution or sedimentation), especially during early life stages. However, not much is known about their response to the interactive effects of ocean warming (OW) and acidification (OA). These drivers can also affect the performance and survival of crustose coralline algae, which are associated understory species likely playing a role in the recruitment of later successional species such as forest-forming macroalgae. We tested the interactive effects of elevated temperature, low pH and species facilitation on the recruitment of Cystoseira compressa. We demonstrate that the interactive effects of OW and OA negatively affect the recruitment of C. compressa and its associated coralline algae Neogoniolithon brassica-florida. The density of recruits was lower under the combinations OW and OA, while the size was negatively affected by the temperature increase but positively affected by the low pH. The results from this study show that the interactive effects of climate change and the presence of crustose coralline algae can have a negative impact on the recruitment of Cystoseira s.l. species. While new restoration techniques recently opened the door to marine forest restoration, our results show that the interactions of multiple drivers and species interactions have to be considered to achieve long-term population sustainability.
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