Levelling-up rhodolith-bed science to address global-scale conservation challenges.

Global marine conservation remains fractured by an imbalance in research efforts and policy actions, limiting progression towards sustainability. Rhodolith beds represent a prime example, as they have ecological importance on a global scale, provide a wealth of ecosystem functions and services, including biodiversity provision and potential climate change mitigation, but remain disproportionately understudied, compared to other coastal ecosystems (tropical coral reefs, kelp forests, mangroves, seagrasses). Although rhodolith beds have gained some recognition, as important and sensitive habitats at national/regional levels during the last decade, there is still a notable lack of information and, consequently, specific conservation efforts. We argue that the lack of information about these habitats, and the significant ecosystem services they provide, is hindering the development of effective conservation measures and limiting wider marine conservation success. This is becoming a pressing issue, considering the multiple severe pressures and threats these habitats are exposed to (e.g., pollution, fishing activities, climate change), which may lead to an erosion of their ecological function and ecosystem services. By synthesizing the current knowledge, we provide arguments to highlight the importance and urgency of levelling-up research efforts focused on rhodolith beds, combating rhodolith bed degradation and avoiding the loss of associated biodiversity, thus ensuring the sustainability of future conservation programs.

Revisiting the 'bank of microscopic forms' in macroalgal-dominated ecosystems.

Theoretical ecological models, such as succession and facilitation, were defined in terrestrial habitats, and subsequently applied to marine and freshwater habitats in intertidal and then subtidal realms. One such model is the soil seed bank, defined as all viable seeds (or fruits) found near the soil surface that facilitate community restoration/recovery. "Banks of microscopic forms" have been hypothesized in aquatic habitats and recent work from aquaculture has highlighted dormancy in algal life cycle stages. To reinvigorate the discussions about these algal banks, we discuss differences in life cycles, dispersal, and summarize research on banks of macroalgal stages in aquatic ecosystems that may be easier to explore with modern advances in molecular technology. With focus on seminal work in global kelp forest ecosystems, we present a pilot study in northern California as proof of concept that Nereocystis luetkeana and Alaria marginata stages can be detected within kelp forests in the biofilm of rocks and bedrock using targeted primers long after zoospore release. Considering the increased interest in algae as an economic resource, [blue] carbon sink, and as ecosystem engineers, the potential for "banking" macroalgal forms could be a mechanism of resilience and recovery in aquatic populations that have complex life cycles and environmental cues for reproduction. Molecular barcoding is becoming an important tool for identifying banks of macroalgal forms in marine communities. Understanding banks of macroalgal stages, especially in deforested habitats with intense disturbance and grazer pressure, will allow researchers and marine resource managers to facilitate this natural process in recovery of the aquatic system.

A review of subtidal kelp forests in Ireland: From first descriptions to new habitat monitoring techniques.

AIM: Kelp forests worldwide are important marine ecosystems that foster high primary to secondary productivity and multiple ecosystem services. These ecosystems are increasingly under threat from extreme storms, changing ocean temperatures, harvesting, and greater herbivore pressure at regional and global scales, necessitating urgent documentation of their historical to present-day distributions. Species range shifts to higher latitudes have already been documented in some species that dominate subtidal habitats within Europe. Very little is known about kelp forest ecosystems in Ireland, where rocky coastlines are dominated by Laminaria hyperborea. In order to rectify this substantial knowledge gap, we compiled historical records from an array of sources to present historical distribution, kelp and kelp forest recording effort over time, and present rational for the monitoring of kelp habitats to better understand ecosystem resilience. LOCATION: Ireland (Northern Ireland and Éire). METHODS: Herbaria, literature from the Linnaean society dating back to late 1700s, journal articles, government reports, and online databases were scoured for information on L. hyperborea. Information about kelp ecosystems was solicited from dive clubs and citizen science groups that are active along Ireland's coastlines. RESULTS: Data were used to create distribution maps and analyze methodology and technology used to record L. hyperborea presence and kelp ecosystems within Ireland. We discuss the recent surge in studies on Irish kelp ecosystems, fauna associated with kelp ecosystems that may be used as indicators of ecosystem health and suggest methodologies for continued monitoring. MAIN CONCLUSIONS: While there has been a steady increase in recording effort of the dominant subtidal kelp forest species, L. hyperborea, only recently have studies begun to address other important eco-evolutionary processes at work in kelp forests including connectivity among kelp populations in Ireland. Further monitoring, using suggested methodologies, is required to better understand the resilience of kelp ecosystems in Ireland.

Arctic Coralline Algae Elevate Surface pH and Carbonate in the Dark.

Red coralline algae are projected to be sensitive to ocean acidification, particularly in polar oceans. As important ecosystem engineers, their potential sensitivity has broad implications, and understanding their carbon acquisition mechanisms is necessary for making reliable predictions. Therefore, we investigated the localized carbonate chemistry at the surface of Arctic coralline algae using microsensors. We report for the first time carbonate ion concentration and pH measurements ([CO3 2-]) at and above the algal surface in the microenvironment. We show that surface pH and [CO3 2-] are higher than the bulk seawater in the light, and even after hours of darkness. We further show that three species of Arctic coralline algae have efficient carbon concentrating mechanisms including direct bicarbonate uptake and indirect bicarbonate use via a carbonic anhydrase enzyme. Our results suggest that Arctic corallines have strong biological control over their surface chemistry, where active calcification occurs, and that net dissolution in the dark does not occur. We suggest that the elevated pH and [CO3 2-] in the dark could be explained by a high rate of light independent carbon fixation that reduces respiratory CO2 release. This mechanism could provide a potential adaptation to ocean acidification in Arctic coralline algae, which has important implications for future Arctic marine ecosystems.

Influences of salinity on the physiology and distribution of the Arctic coralline algae, Lithothamnion glaciale (Corallinales, Rhodophyta).

In Greenland, free-living red coralline algae contribute to and dominate marine habitats along the coastline. Lithothamnion glaciale dominates coralline algae beds in many regions of the Arctic, but never in Godthåbsfjord, Greenland, where Clathromorphum sp. is dominant. To investigate environmental impacts on coralline algae distribution, calcification and primary productivity were measured in situ during summers of 2015 and 2016, and annual patterns of productivity in L. glaciale were monitored in laboratory-based mesocosm experiments where temperature and salinity were manipulated to mimic high glacial melt. The results of field and cold-room measurements indicate that both L. glaciale and Clathromorphum sp. had low calcification and photosynthetic rates during the Greenland summer (2015 and 2016), with maximum of 1.225 ± 0.17 or 0.002 ± 0.023 µmol CaCO3  · g-1  · h-1 and -0.007 ±0.003 or -0.004 ± 0.001 mg O2  · L-1  · h-1 in each species respectively. Mesocosm experiments indicate L. glaciale is a seasonal responder; photosynthetic and calcification rates increase with annual light cycles. Furthermore, metabolic processes in L. glaciale were negatively influenced by low salinity; positive growth rates only occurred in marine treatments where individuals accumulated an average of 1.85 ± 1.73 mg · d-1 of biomass through summer. These results indicate high freshwater input to the Godthåbsfjord region may drive the low abundance of L. glaciale, and could decrease species distribution as climate change increases freshwater input to the Arctic marine system via enhanced ice sheet runoff and glacier calving.

Structure and Function of Macroalgal Natural Products.

Since the initial discovery of marine phyco-derived secondary metabolites in the 1950s there has been a rapid increase in the description of new algal natural products. These metabolites have multiple ecological roles as well as commercial value as potential drugs or lead compounds. With the emergence of resistance to our current arsenal of drugs as well as the development of new chemotherapies for currently untreatable diseases, new compounds must be sourced. As outlined in this chapter algae produce a diverse range of chemicals many of which have potential for the treatment of human afflictions.In this chapter we outline the classes of metabolites produced by this chemically rich group of organisms as well as their respective ecological roles in the environment. Algae are found in nearly every environment on earth, with many of these organisms possessing the ability to shape the ecosystem they inhabit. With current challenges to climate stability, understanding how these important organisms interact with their environment as well as one another might afford better insight into how they respond to a changing climate.