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The chapter describes the geology, oceanography, and patterns of biogeography of the California kelp forests. The structure and biodiversity of the kelp forest food web for all trophic guilds is described as well as findings from experimental manipulations and long time series studies. The chapter finishes with a discussion of the role of fishing, habitat loss, and climate change on these kelp forests.

This chapter reviews coastal benthic communities with the aim of deriving a global estimate for respiration in these ecosystems. Reefs, mangroves, salt marshes, macroalgae, sea grasses, and unvegetated sediments dominate respiration in the coastal ocean. Estimates of coastal benthic respiration are not well constrained but converge on about 620 Tmol C/a. In coastal benthic ecosystems, autotrophs and multicellular heterotrophs contribute significantly to, and in some systems even dominate respiration unlike in most other oceanic ecosystems in which bacteria dominate respiration.

Most rocky intertidal zone field studies require quantification of abundance, of either individual species or other taxonomic units of the investigator's choice. Data indicating species abundances can be collected quickly using subjective scales or by determining the presence of species in defined sampling units. This chapter reviews various methods of quantifying the density and cover of rocky intertidal populations using nondestructive sampling procedures. It discusses procedures used to collect abundance data during rapid surveys and while using plotless and line transect sampling methods. It focuses on plot- or quadrat-based methods for determining density and cover of intertidal macroalgae and macroinvertebrates. Differences between plots and quadrats are somewhat semantic and the terms are used as functional synonyms in this chapter.

Archaeologically, the use of marine kelps and seaweeds is poorly understood, yet California's islands are surrounded by extensive and highly productive kelp forests with nearshore habitats containing more than 100 edible species. Historical accounts from around the Pacific Rim demonstrate considerable use of seaweeds and seagrasses by native people, but there has been little discussion of seaweeds as a potential food source on California's islands. This chapter summarizes the biology, diversity, ecology, and productivity of marine macroalgae and marine angiosperms in the California Bight, supporting the likely consumption of seaweeds in the past. The potential use of plentiful and nutritious seaweeds by California Island peoples has major implications for the perceived marginality of the islands.

This chapter focuses on the recent and emerging research involving chemical defences against herbivory in aquatic primary producers. It provides an overview of plant chemical defence theories and highlights recent research on aquatic primary producers addressing a number of aspects of these theories, concluding with new chemical approaches to tackle the questions and suggestions for future research directions. It explains that aquatic primary producers are a taxonomically and functionally diverse group of organisms that includes macroalgae, microalgae, and vascular plants. It also states that despite the fact that aquatic primary producers constitute a large and diverse group of organisms that vary in their evolutionary histories, selection for chemical defences to resist or reduce grazing are commonplace across the phylogenetic boundaries.

In this chapter the general processes involved in controlling production and transformation of organic matter will be discussed as well as some of the associated stoichiometric changes of a few key biological elements (e.g., C, N, P, S). Stoichiometry is defined as the mass balance of chemical reactions as they relate to the law of definite proportions and conservation of mass (Sterner and Elser, 2002). For example, if we examine the average atomic ratios of C, N, and P in phytoplankton we see a relatively consistent ratio of 106:16:1 in most marine species. This is perhaps the best example of applied stoichiometric principles in natural ecosystems and is derived from the classic work of Alfred C. Redfield (1890–1983) (Redfield, 1958; Redfield et al., 1963). More specifically, Redfield compared the ratios of C, N, and P of dissolved nutrients in marine waters to that of suspended marine particulate matter (seston) (essentially phytoplankton) and found straight lines with equal slopes (figure 8.1; Redfield et al., 1963). This relationship suggested that marine biota were critical in determining the chemistry of the world ocean, clearly one of the most important historical findings linking chemical and biological oceanography (Falkowski, 2000). Moreover, the Redfield ratio has been further validated with recent data using improved analytical techniques (Karl et al., 1993; Hoppema and Goeyens, 1999). Other work has shown that there are predictable deviations from the Redfield ratio across a freshwater to open ocean marine gradient (figure 8.2; Downing, 1997). For example, N-to-P ratios in estuaries have commonly been shown to be lower and/or higher than the predicted Redfield ratio because of denitrification and anthropogenic nutrient enrichment processes, respectively. Inputs of vascular plant organic matter (e.g., mangroves, salt marshes, seagrasses) to estuarine systems presents another problem in causing deviations of C:N:P from the Redfield ratio. Vascular plants have been shown to deviate from this ratio in part because of relatively high amounts of C and N compared to algae due to a higher abundance of structural support molecules (e.g., cellulose, lignin) and defense antiherbivory (secondary) compounds (e.g., tannins), respectively (Vitousek et al., 1988).