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This chapter looks at the elements from the penultimate group of the periodic table—the halogens (‘salt-formers’). We shall see that the first of these elements was discovered by Scheele during his investigations of the mineral pyrolusite. Lavoisier knew of the element but he failed to recognize it as such since he was convinced the gas had to contain oxygen and so must be a compound. It was left to Davy to prove that this was not so, which led to the English chemist naming this element that had been discovered (but not properly named) over thirty years before by the great Scheele. Davy’s choice was to influence the names given to all the members of this group, including the most recent member named in 2016. There are three common acids known as mineral acids, since they may all be obtained by heating combinations of certain minerals. Their modern names are nitric acid, sulfuric acid, and hydrochloric acid. Of these three, hydrochloric was probably the last to be discovered. Nitric and sulfuric acids were obtained in the thirteenth or early fourteenth centuries, but the earliest unambiguous preparation of relatively pure hydrochloric acid is from a hundred years later, in a manuscript from Bologna which translates as Secrets for Colour. It gives a curious recipe for a water to soften bones: ‘Take common salt and Roman vitriol in equal quantities, and grind them very well together; then distil them through an alembic, and keep the distilled water in a vessel well closed.’ As we saw in Chapter 3, ‘Roman vitriol’ is a hydrated metal sulfate, probably iron or copper sulfate; its mixture with salt, when heated, produces water and hydrogen chloride, which together form the acid solution. Later texts from the sixteenth and seventeenth centuries include similar methods to prepare this so-called spirit of salt, or ‘oyle of salt’. The first mentioned use, to soften bones, is indeed best achieved with hydrochloric acid, which readily dissolves the minerals from bone to leave only the organic matter largely intact. Leave a chicken bone in dilute hydrochloric acid for a few hours, and it may easily be bent without breaking.

Species abundances in rocky intertidal zones are generally expressed as numerical density or counts as cover. Occasionally, however, the goals of a sampling program require that the biomass of rocky intertidal organisms are determined and used to express abundance. Biomass is defined as the mass of living organisms in a population at the time of sampling. Unlike density determinations, which require the ability of the investigators to distinguish individual organisms, biomass can be measured for all seaweeds and invertebrates. This chapter describes a procedure for harvesting large seaweeds and macroinvertebrates from field plots.

Most rocky intertidal zone monitoring and impact studies are designed to determine the status of sampled populations solely in terms of abundance. This approach can present two problems. First, abundance data alone do not adequately describe a population in a way that depicts its dynamics. Population density is a result of primary and secondary population parameters. A second problem involves the high “noise-to-signal” ratio because of the usual high variation obtained when sampling for abundance data or other population-based parameters. This chapter describes selected approaches for measuring secondary population parameters in rocky intertidal organisms. It focuses on procedures used to determine age and class size distributions, growth rates, sex or phase ratios, and reproduction in seaweeds and benthic invertebrates.

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.

Our diet affects our physiology. People who can drink milk as adults have evolved different physiologies from those who cannot. The same is true of people who live on starch. Only the Japanese can digest seaweed, again for essentially the same reason, namely adaptation. Peoples from different regions are differently susceptible to a variety of drugs, including alcohol. Genetic differences underlie several of the contrasting susceptibilities, but the degree to which this variation is due to adaptation or chance mutation still has to be determined. Arctic peoples' ability to eat amounts of fat that would probably make others ill is explained not by genes, but by a lifetime of a fatty diet, along with, in the past, a healthy lifestyle.