Body size is manifestly one of the most important attributes of an organism from an ecological and evolutionary point of view. Size has a predominant influence on an animal's energetic requirements, its potential for resource exploitation, and its susceptibility to natural enemies. A large literature now exists on how physiological, life history, and population parameters scale with body dimensions (24, 131). The ecological literature on species interactions and the structure of animal communities also stresses the importance of body size. Differences in body size are a major means by which species avoid direct overlap in resource use (153), and size-selective predation can be a primary organizing force in some communities (20, 70). Size thus imposes important constraints on the manner in which an organism interacts with its environment and influences the strength, type, and symmetry of interactions with other species (152, 207). Paradoxically, ecologists have virtually ignored the implications of these observations for interactions among species that exhibit size-distributed populations. For instance, it has been often suggested that competing species

https://www.jstor.org/stable/pdf/2096954.pdf

The ontogenetic niche and species interactions in size-structured populations

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

Mussels attach to solid surfaces in the sea. Their adhesion must be rapid, strong, and tough, or else they will be dislodged and dashed to pieces by the next incoming wave. Given the dearth of synthetic adhesives for wet polar surfaces, much effort has been directed to characterizing and mimicking essential features of the adhesive chemistry practiced by mussels. Studies of these organisms have uncovered important adaptive strategies that help to circumvent the high dielectric and solvation properties of water that typically frustrate adhesion. In a chemical vein, the adhesive proteins of mussels are heavily decorated with Dopa, a catecholic functionality. Various synthetic polymers have been functionalized with catechols to provide diverse adhesive, sealant, coating, and anchoring properties, particularly for critical biomedical applications.

Mussel-Inspired Adhesives and Coatings

We provide a brief synopsis of the unique physical and ecological attributes of sandy beach ecosystems and review the main anthropogenic pressures acting on the world's single largest type of open shoreline. Threats to beaches arise from a range of stressors which span a spectrum of impact scales from localised effects (e.g. trampling) to a truly global reach (e.g. sea-level rise). These pressures act at multiple temporal and spatial scales, translating into ecological impacts that are manifested across several dimensions in time and space so that today almost every beach on every coastline is threatened by human activities. Press disturbances (whatever the impact source involved) are becoming increasingly common, operating on time scales of years to decades. However, long-term data sets that describe either the natural dynamics of beach systems or the human impacts on beaches are scarce and fragmentary. A top priority is to implement long-term field experiments and monitoring programmes that quantify the dynamics of key ecological attributes on sandy beaches. Because of the inertia associated with global climate change and human population growth, no realistic management scenario will alleviate these threats in the short term. The immediate priority is to avoid further development of coastal areas likely to be directly impacted by retreating shorelines. There is also scope for improvement in experimental design to better distinguish natural variability from anthropogenic impacts. Sea-level rise and other effects of global warming are expected to intensify other anthropogenic pressures, and could cause unprecedented ecological impacts. The definition of the relevant scales of analysis, which will vary according to the magnitude of the impact and the organisational level under analysis, and the recognition of a physical–biological coupling at different scales, should be included in approaches to quantify impacts. Zoning strategies and marine reserves, which have not been widely implemented in sandy beaches, could be a key tool for biodiversity conservation and should also facilitate spillover effects into adjacent beach habitats. Setback and zoning strategies need to be enforced through legislation, and all relevant stakeholders should be included in the design, implementation and institutionalisation of these initiatives. New perspectives for rational management of sandy beaches require paradigm shifts, by including not only basic ecosystem principles, but also incentives for effective governance and sharing of management roles between government and local stakeholders.

/pdf/threats-to-sandy-beach-ecosystems-a-review-50zdg3kglj.pdf

Threats to sandy beach ecosystems: A review

A taxonomic account of the world's kelps is far too complex for the scope of this review, but Mann (146) has characterized the world's kelp forests by their dominant genera. Laminaria species are found in many parts of the world but dominate both sides of the Atlantic and the coasts of China and Japan. Ecklonia dominates some kelp forests in Australia, New Zealand, South Africa, and a few other southern hemisphere localities. The giant kelp, Macrocystispyrifera, forms dense forests in many parts of the world including areas of the northeast Pacific, the southern shores of South America, many Southern Ocean islands, and isolated areas of South Africa, Australia, and New Zealand. Macrocystis pyrifera does not occur in the eastern Pacific area north of San Francisco, California; however, this northern region has the highest species diversity of kelps in the world (63), with Macrocystis integrifolia and Nereocystis, Alaria, Pterygophora, and Laminaria, among other conspicuous genera.

Ecology of Kelp Communities

Description: This unrivalled field guide covers over 1,400 species of the most common forms of marine life that inhabit our coasts'including the invertebrates, fish, reptiles, mammals birds and plants. The book documents a selection of these, concentrating on the most frequently encountered species living in the intertidal zone and in shallow subtidal waters that can readily be explored by scuba divers. There is a particular focus on open-coast beaches and rocky shores, and aquatic estuarine animals and plants are also covered. Fish that are commonly seen in tidal pools or by divers, or those frequently caught by angers are included, as are smaller rock-pool fish. It will meet the needs of scientists, students, fishermen, scuba divers and beachcombers alike, encapsulating current knowledge and enabling the identification of diverse species, from sponges to whales and from seaweeds to mangroves.

Two oceans: A guide to the marine life of southern Africa

The current status of marine alien species along the South African coast is reviewed and the ecological and economic impacts of these invasions are discussed. In all, 10 confirmed extant alien and 22 cryptogenic species are recorded from the region. All 10 alien species support well-established populations and the majority of these remain restricted in distribution to sheltered bays, estuaries and harbours. Only one species, the Mediterranean mussel Mytilus galloprovincialis, has spread extensively along the coast and caused significant ecological impacts. These include the competitive displacement of indigenous species and a dramatic increase in intertidal mussel biomass. These changes have also increased available habitat for many infaunal species and resulted in enhanced food supply for intertidal predators. Considerable economic benefits have also resulted from this invasion because M. galloprovincialis forms the basis of the South African mussel culture industry.

/pdf/marine-alien-species-of-south-africa-status-and-impacts-3fk7uwk3lr.pdf

Marine alien species of South Africa — status and impacts

Continental South Africa has a coastline of some 3,650 km and an Exclusive Economic Zone (EEZ) of just over 1 million km2. Waters in the EEZ extend to a depth of 5,700 m, with more than 65% deeper than 2,000 m. Despite its status as a developing nation, South Africa has a relatively strong history of marine taxonomic research and maintains comprehensive and well-curated museum collections totaling over 291,000 records. Over 3 million locality records from more than 23,000 species have been lodged in the regional AfrOBIS (African Ocean Biogeographic Information System) data center (which stores data from a wider African region). A large number of regional guides to the marine fauna and flora are also available and are listed.

The currently recorded marine biota of South Africa numbers at least 12,914 species, although many taxa, particularly those of small body size, remain poorly documented. The coastal zone is relatively well sampled with some 2,500 samples of benthic invertebrate communities have been taken by grab, dredge, or trawl. Almost none of these samples, however, were collected after 1980, and over 99% of existing samples are from depths shallower than 1,000 m—indeed 83% are from less than 100 m. The abyssal zone thus remains almost completely unexplored.

South Africa has a fairly large industrial fishing industry, of which the largest fisheries are the pelagic (pilchard and anchovy) and demersal (hake) sectors, both focused on the west and south coasts. The east coast has fewer, smaller commercial fisheries, but a high coastal population density, resulting in intense exploitation of inshore resources by recreational and subsistence fishers, and this has resulted in the overexploitation of many coastal fish and invertebrate stocks. South Africa has a small aquaculture industry rearing mussels, oysters, prawns, and abalone—the latter two in land-based facilities.

Compared with many other developing countries, South Africa has a well-conserved coastline, 23% of which is under formal protection, however deeper waters are almost entirely excluded from conservation areas. Marine pollution is confined mainly to the densely populated KwaZulu-Natal coast and the urban centers of Cape Town and Port Elizabeth. Over 120 introduced or cryptogenic marine species have been recorded, but most of these are confined to the few harbors and sheltered sites along the coast.

https://open.uct.ac.za/bitstream/handle/11427/16080/Griffiths_Marine_Biodiversity_in_South_Africa_2010.pdf;sequence=1

Marine biodiversity in South Africa: an evaluation of current states of knowledge.

The guide intends to facilitate the identification of the most common forms of marine life that inhabit southern African coasts. Invertebrates, fish, reptiles, mammals and plants, are included. In particular, focus is on the life of open coast beaches and rocky shores, and the most frequently encountered species that live in the intertidal zone and in shallow subtidal waters that can be readily explored by scuba-divers are covered. More than 1400 species are included, being presented in taxonomic groups according to the classification system of the animal and plant kingdoms. Most species are illustrated with colour photographs, and descriptive notes are given regarding identification, size, biology, maps, and related species.

Two Oceans : A Guide to the Marine Life of Southern Africa

Up to 12 marine mollusc and three crab species are thought to have been deliberately or accidentally introduced to South Africa. Of these, only the Mediterranean mussel Mytilus galloprovincialis and the European shore crab Carcinus meanas have become invasive. M. galloprovincialis, probably introduced in the late 1970s, is already the dominant mussel throughout the Cape west coast. As a result, indigenous intertidal mussels Aulacomya ater have been largely displaced, mussel standing stock has increased and the upshore limit of mussel beds has become considerably elevated. Implications include competitive exclusion of large limpets but enhanced recruitment of juvenile limpets, increased habitat availability for mussel infauna, reduction of habitat for algal infauna and enhanced food availability for predators, particularly terrestrial species. C. maenas was first recorded from Table Bay Docks in 1983 and currently ranges from Camps Bay to Saldanha Bay. Although it is a voracious predator, it appears unable...

Charles L. Griffiths

Papers

Two oceans: A guide to the marine life of southern Africa

Marine alien species of South Africa — status and impacts

Marine biodiversity in South Africa: an evaluation of current states of knowledge.

Two Oceans : A Guide to the Marine Life of Southern Africa

Marine invasive aliens on South African shores: implications for community structure and tropillc functioning