Edgar outlines the physical structure of each habitat and the biophysical constraints placed on life.
"The two most important physical factors affecting the shoreline are wave action and the underlying rock type. Sandy beaches erode to bedrock when exposed to extreme wave action, so typically occur in regions with moderate rather than high wave energy or gradual offshore slopes. ..."This often involves keystone species such as mangroves and seagrasses.
Next comes a survey of the organisms found in the habitat. This emphasises trophic interactions between species; each chapter includes a diagrammatic food web.
"Bottom-dwelling or benthic invertebrates are often sub-divided into several major categories, depending on food preferences. Herbivorous, carnivorous and scavenging species are all found living in soft sediments but are generally less abundant than two groups that consume fine particles — the detritivores and the suspension feeders."(References to particular species are usually to Australian species; geographical locations are similarly specific. But there are comparisons to other temperate marine environments and most of the discussion is general.)
Each chapter concludes with one or two pages on an environmental issue: the introduction of foreign species, sewage, oil spills, coastal development, beach litter, overfishing, nutrients and turbidity, harvesting of intertidal animals, toxic chemicals and heavy metals, and global warming.
Australian Marine Habitats is well illustrated with colour photographs, with every second pair of pages a photo-spread, and could be enjoyed just for these. But it comes with full references into the scientific literature — in the form of endnotes with page/paragraph numbers, so nothing intrudes into the text — as well as a glossary and an index, and would make a fine textbook. And even the photographs have captions that are not just descriptive, but informative of broader science.
"The majority of fishes living on soft sediments possess mottled grey or pink bodies that blend in with the seabed at depth. Such a pattern acts as camouflage from predators and prevents early detection by prey. Gurnards and species in a number of other fish families also possess strongly contrasting fins that can be hidden or raised to signal competitors and mates. (Lepidotrigla vanessa)"
Australian Marine Habitats is a splendid work — one which should appeal to everyone from casual visitors to Australian coastlines to students and professionals who need an introduction to marine ecology.