The conservation and sustainable use of marine resources is a highlighted goal on a growing number of national and international policy agendas. Unfortunately, efforts to assess progress, as well as to strategically plan and prioritize new marine conservation measures, have been hampered by the lack of a detailed, comprehensive biogeographic system to classify the oceans. Here we report on a new global system for coastal and shelf areas: the Marine Ecoregions of the World, or MEOW, a nested system of 12 realms, 62 provinces, and 232 ecoregions. This system provides considerably better spatial resolution than earlier global systems, yet it preserves many common elements and can be cross-referenced to many regional biogeographic classifications. The designation of terrestrial ecoregions has revolutionized priority setting and planning for terrestrial conservation; we anticipate similar benefits from the use of a coherent and credible marine system.

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Marine Ecoregions of the World: A Bioregionalization of Coastal and Shelf Areas

Kelp forests are phyletically diverse, structurally complex and highly productive components of coldwater rocky marine coastlines. This paper reviews the conditions in which kelp forests develop globally and where, why and at what rate they become deforested. The ecology and long archaeological history of kelp forests are examined through case studies from southern California, the Aleutian Islands and the western North Atlantic, well-studied locations that represent the widest possible range in kelp forest biodiversity. Global distribution of kelp forests is physiologically constrained by light at high latitudes and by nutrients, warm temperatures and other macrophytes at low latitudes. Within mid-latitude belts (roughly 40–60° latitude in both hemispheres) well-developed kelp forests are most threatened by herbivory, usually from sea urchins. Overfishing and extirpation of highly valued vertebrate apex predators often triggered herbivore population increases, leading to widespread kelp deforestation. Such deforestations have the most profound and lasting impacts on species-depauperate systems, such as those in Alaska and the western North Atlantic. Globally urchin-induced deforestation has been increasing over the past 2–3 decades. Continued fishing down of coastal food webs has resulted in shifting harvesting targets from apex predators to their invertebrate prey, including kelp-grazing herbivores. The recent global expansion of sea urchin harvesting has led to the widespread extirpation of this herbivore, and kelp forests have returned in some locations but, for the first time, these forests are devoid of vertebrate apex predators. In the western North Atlantic, large predatory crabs have recently filled this void and they have become the new apex predator in this system. Similar shifts from fish- to crab-dominance may have occurred in coastal zones of the United Kingdom and Japan, where large predatory finfish were extirpated long ago. Three North American case studies of kelp forests were examined to determine their long history with humans and project the status of future kelp forests to the year 2025. Fishing impacts on kelp forest systems have been both profound and much longer in duration than previously thought. Archaeological data suggest that coastal peoples exploited kelp forest organisms for thousands of years, occasionally resulting in localized losses of apex predators, outbreaks of sea urchin populations and probably small-scale deforestation. Over the past two centuries, commercial exploitation for export led to the extirpation of sea urchin predators, such as the sea otter in the North Pacific and predatory fishes like the cod in the North Atlantic. The large-scale removal of predators for export markets increased sea urchin abundances and promoted the decline of kelp forests over vast areas. Despite southern California having one of the longest known associations with coastal kelp forests, widespread deforestation is rare. It is possible that functional redundancies among predators and herbivores make this most diverse system most stable. Such biodiverse kelp forests may also resist invasion from non-native species. In the species-depauperate western North Atlantic, introduced algal competitors carpet the benthos and threaten future kelp dominance. There, other non-native herbivores and predators have become established and dominant components of this system. Climate changes have had measurable impacts on kelp forest ecosystems and efforts to control the emission of greenhouse gasses should be a global priority. However, overfishing appears to be the greatest manageable threat to kelp forest ecosystems over the 2025 time horizon. Management should focus on minimizing fishing impacts and restoring populations of functionally important species in these systems.

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Kelp forest ecosystems: biodiversity, stability, resilience and future

Algal–bacterial processes for the treatment of hazardous contaminants: A review

Production and harvesting of microalgae for wastewater treatment, biofuels, and bioproducts

Ocean acidification represents a key threat to coral reefs by reducing the calcification rate of framework builders. In addition, acidification is likely to affect the relationship between corals and their symbiotic dinoflagellates and the productivity of this association. However, little is known about how acidification impacts on the physiology of reef builders and how acidification interacts with warming. Here, we report on an 8-week study that compared bleaching, productivity, and calcification responses of crustose coralline algae (CCA) and branching (Acropora) and massive (Porites) coral species in response to acidification and warming. Using a 30-tank experimental system, we manipulated CO2 levels to simulate doubling and three- to fourfold increases [Intergovernmental Panel on Climate Change (IPCC) projection categories IV and VI] relative to present-day levels under cool and warm scenarios. Results indicated that high CO2 is a bleaching agent for corals and CCA under high irradiance, acting synergistically with warming to lower thermal bleaching thresholds. We propose that CO2 induces bleaching via its impact on photoprotective mechanisms of the photosystems. Overall, acidification impacted more strongly on bleaching and productivity than on calcification. Interestingly, the intermediate, warm CO2 scenario led to a 30% increase in productivity in Acropora, whereas high CO2 lead to zero productivity in both corals. CCA were most sensitive to acidification, with high CO2 leading to negative productivity and high rates of net dissolution. Our findings suggest that sensitive reef-building species such as CCA may be pushed beyond their thresholds for growth and survival within the next few decades whereas corals will show delayed and mixed responses.

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Ocean acidification causes bleaching and productivity loss in coral reef builders

The crustose coralline algae are well known in shallow tropical waters as reef frame-builders and sediment producers. Although their abundance at greater depths and in arctic waters has been previously recorded, this knowledge in recent decades has been largely ignored by geologists and marine scientists in general. Many erroneous or misleading ecological and paleoecological statements and conclusions have resulted, and we have endeavored to clarify matters through the citation of the older literature along with more recent ecological studies.

A parallel tendency to “simplify” the taxonomic structure of crustose corallines has threatened to add considerable confusion to modern marine studies. We have discussed recent work on anatomy, reproduction, and taxonomy. These and classical data are summarized in the form of keys and an evolutionary tree, which are intended to provide the geologist and marine biologist with a working facility with the group.

A number of quantitative ecological studies treating crustose corallines have appeared during the past decade; these results are discussed and possibilities for future ecological work indicated. The occurrence of rhodoliths (maerl, free corallines) and the factors controlling the development of these deposits are also noted.

Crustose Coralline Algae: A Re-evaluation in the Geological Sciences

Review—coral reefs: algal structured and mediated ecosystems in shallow, turbulent, alkaline waters

Windward reef morphogenesis is a dynamic process directly controlled by the growth potential of dominant corals and coralline algae relative to wave energy and sea level rise. Moderate wave energy favors vertically rapid growth that is porous and uncemented; high wave energy favors slow but compact growth. Growth potentials of Caribbean and Indo-Pacific reefs are probably equivalent. Major differences are probably not due to biological or direct climatic factors but are in part related to differing patterns of sea level rise resulting from Holocene crustal adjustment. The nature and position of antecedent foundations developed by high interglacial and interstadial sea levels is especially critical and is largely controlled by regional tectonic factors, especially long-term subsidence.

https://science.sciencemag.org/content/sci/202/4370/831.full.pdf

Coral Reef Morphogenesis: A Multidimensional Model

Crustose corallines were collected from a wide range of depths (intertidal to about 300 m) throughout the Hawaiian Archipelago. A total of 25 species in 10 genera are recognized on the basis of habit, anatomy, morphology, and ecology, including one new genus and 10 new species. Generic and specific keys for the differentiation of the Hawaiian crustose corallines are also provided.The ecology of each species, in terms of depth distribution and habitat, is also given, and the potential use of these plants in determining paleoenvironments in the Hawaiian Neogene is discussed.The Caribbean and Hawaiian crustose coralline floras are briefly compared. The large number of "pair species" and the parallelism in subfamily, generic, and "pair species" ecology indicate that coralline evolution is very slow. The crustose corallines are potentially excellent paleoecological indicators for the Tertiary.

The crustose coralline algae (Rhodophyta, Corallinaceae) of the Hawaiian Islands

The effect of amphipod grazing on algal community structure was studied within a 75 l refuge tank connected to a 6500 l closed-system, coral reef microcosm. When amphipods (Ampithoe ramondi) were absent or present in low numbers, a high biomass of mostly filamentous algal species resulted, including Bryopsis hypnoides, Centroceras clavulatum, Ceramium flaccidum, Derbesia vaucheriaeformis, Enteromorpha prolifera, Giffordia rallsiae, and Polysiphonia havanensis. These microalgae disappeared when amphipod density increase beyond approximately 1 individual cm-2 of tank surface. The macroalga Hypnea spinella germinated in the system in association with amphipod tube sites. H. spinella plants remained rare until filamentous species were eliminated by amphipod grazing. Feeding trials confirmed that H. spinella was protected from grazing by its size rather than a chemical defense strategy. The H. spinella community we observed is similar to the flora described on algal ridges where physical conditions exclude fish grazing. We suggest that amphipods and similar micrograzers are responsible for the algal community structure of these ridges. Caging experiments may be subject to similar effects from increased amphipod grazing on the algae. Introduction of fish that are amphipod predators into the refuge tank caused an increase in algal species diversity but total H. spinella growth rates fell from 25 g dry wt month-1 to less than 8 g dry wt month-1. We describe amphipod behavior in relation to changes in population density and food supply, and we stress the potential for increasing the productivity of commercial seaweeds through maintenance of appropriate amphipod species in mariculture facilities.

Walter H. Adey

Papers

Crustose Coralline Algae: A Re-evaluation in the Geological Sciences

Review—coral reefs: algal structured and mediated ecosystems in shallow, turbulent, alkaline waters

Coral Reef Morphogenesis: A Multidimensional Model

The crustose coralline algae (Rhodophyta, Corallinaceae) of the Hawaiian Islands

The effect of micrograzers on algal community structure in a coral reef microcosm