Is bull-kelp kelp? The role of common names in science

Abstract

Common names are non-specific by definition, and scientists should naturally avoid placing strict rules on their usage. There are many examples of common names applying to numerous, often only distantly related taxa, yet the term ‘kelp’ is increasingly being used to refer solely to members of the macroalgal order Laminariales, and some scientists now assert that any other use is incorrect. A brief examination of the word's etymology, however, demonstrates that kelp can with equal validity also refer to non-laminarialean taxa. Many people do still use the word ‘kelp’ in its broader sense, and these conflicting definitions of the word can lead to confusion and miscommunication between scientists and the general public. This review demonstrates that the definition of ‘kelp’ should remain relaxed, in accordance with its role as a common name.

Keywords:

• word
• term
• Laminariales
• Fucales
• macroalga

Introduction

The purpose of scientific (Linnaean) nomenclature is to provide a unique and unambiguous name for each biological taxon. In contrast, common names are not necessarily unique, and are often given to more than one taxon (e.g. Campbell et al. 2009, p. 537). Common names nonetheless play a critical role in science and society, particularly as they are generally considerably easier to remember and pronounce than scientific names. They also often have cultural relevance; for example, European migrants arriving in America, Australia and New Zealand named many species after those in Europe, such as ‘beech’ trees (genus Fagus in the Northern Hemisphere and—in a different family—the genus Nothofagus in the Southern Hemisphere), ‘robins’ (e.g. Turdus migratorius in North America, Petroica australis in New Zealand and Erithacus rubecula in Europe), and ‘smelt’ (fish of the family Osmeridae in Europe, but the family Retropinnidae in Australia/New Zealand) (McDowall 1996). Such terms are unlikely to cause much confusion when used in context, and are easily recognisable; for example, it is perhaps more practical for a child in New Zealand to think of small birds as robins, which feature prominently in many children's books, than as Petroica australis. Even in scientific literature, common names that apply to multiple taxa need not be avoided, provided that the scientific names are also supplied; for example, recent papers on New Zealand robins generally refer to the birds simply as ‘robins’ once the scientific and common names have been defined (e.g. Taylor et al. 2008; Jamieson et al. 2009).

The common term ‘kelp’ has historically been used to refer to almost any large, brown, marine macroalga. Although many still consider this an appropriate definition, there is a growing trend in phycological and marine ecological literature to insist that the term be used to refer only to members of the phaeophycean order Laminariales. For example, some scientists now assert that the term ‘kelp’ applies exclusively to the Laminariales when used in the ‘true’ sense (e.g. Estes & Steinberg 1988; Steneck et al. 2002; Schiel & Foster 2006; Santelices 2007), the ‘strict sense’ (e.g. Bolton 2010) or ‘technically’ (e.g. Dayton 1985). Indeed, Bolton (2010) recently suggested that Fraser et al.'s (2009) use of the word kelp to refer to a non-laminarialean taxon, Durvillaea (also known as ‘southern bull-kelp’, common along the southern coasts of New Zealand), was inappropriate and confusing. Unfortunately, such assertions carry the implication that the use of this word for anything but members of the Laminariales is incorrect. Given the uncertainty regarding the proper usage of this common word, it seems timely to review both its etymology and the role of common names in science.

Origin and early uses of ‘kelp’

According to the second edition of Oxford English Dictionary (OED), the origin of the word ‘kelp’ is not known, but is believed to be late Middle English (OED cites a reference from 1387 to the word ‘culpes’ for seaweed) (OED 1989). The dictionary defines the word generally as:

a collective name for large seaweeds (chiefly Fucaceæ and Laminariaceæ) which are burnt for the sake of the substances found in the ashes.

Throughout the nineteenth century, ‘kelp’ was used to describe the ash produced by both laminarialean or fucalean seaweeds used in the production of sodium carbonate (Gifford 1853; Newton 1931; Chapman 1945, 1970). Newton (1931) writes that such ash was produced by the burning of Laminaria, Ascophyllum, and Fucus species (the latter two being fucalean, not laminarialean, taxa). Chapman (1970, p. 24; see also Trainor 1978, pp. 205, 444) wrote extensively on the early kelp industry, stating in his opening line that:

the word ‘kelp’ in Europe refers primarily to the burnt ash of seaweeds, and it has only subsequently been extended to apply to the actual seaweeds themselves. In America, however, the large brown seaweeds are regularly known as kelps as well as the ash that is prepared from them … 

Chapman (1970, p. 25) states that this use of phaeophycean seaweeds to produce ash for soda (for pottery and glassmaking industries) began in the 17th century in France, and that:

by 1692 the industry was so important that Louis XIV gave … sole privilege of cutting … all the ‘kelp’ weeds (fucoids and laminarians) along the coast of La Hogue … to the glass manufacturers.

Early use of the word was, therefore, certainly not restricted to the Laminariales.

Current use of ‘kelp’

The word ‘kelp’ is currently often used by phycologists and some marine ecologists to refer only to members of the order Laminariales. This definition appears to have come into use in the early 1900s, perhaps shortly after the order Laminariales was erected: whereas in the 1800s ‘kelp’ was still used to refer to the ash produced by burning fucalean or laminarialean seaweeds (e.g. Murray 1895), and the seaweeds themselves (e.g. Darwin 1839; Gifford 1853), by the 1930s some were applying the term exclusively to the Laminariales (e.g. Smith 1938), and modern phycological textbooks also often follow this definition (e.g. Bold & Wynne 1985; Sze 1993; Lee 1999). General use of the word, however, has continued to apply to a broader range of brown macroalgae (Table 1). The common names of some non-laminarialean species surely promote such usage (e.g. ‘southern bull-kelp’ for Durvillaea; and ‘kelp’ or ‘kelpware’ as some of the many common names for Fucus vesiculosus), as does use of the word by the general public. In his introductory book Seaweeds, Thomas (2002, p. 14) writes that:

For many people it is the larger brown species, often referred to as ‘kelps’, that best conjure up the image of seaweed. These seaweeds, including Alaria, Laminaria, Ecklonia and Durvillaea, are several metres long with large leathery fronds held on slender, flexible stalks …

Beyond the field of phycology, many scientists do still use the word ‘kelp’ to refer to almost any large, brown macroalga (including species in phylogenetically distinct orders such as the Fucales and Desmarestiales, as well as the Laminariales; Fig. 1). Dayton (1985), in a review of kelp community ecology, recognised this when he stated in his opening paragraph that:

large brown algae in the order Laminariales and Fucales … are commonly referred to as kelps, although the term technically refers to Laminariales only.

In medical research, ‘kelp’ is frequently used to refer to the fucalean genus Fucus (e.g. Skibola 2004; Haller et al. 2005; Skibola et al. 2005; Jordan & Haywood 2007). In various natural sciences, too, researchers refer to fucalean taxa as kelp (e.g. Kendziorek & Stekoll 1984; Weslawski et al. 1993; Simms 2003; Tarakhovskaya & Maslov 2005). Such use of ‘kelp’ is particularly common in relation to the fucalean genus Durvillaea, which has the common name ‘southern bull-kelp’ but which many scientists have tended to refer to simply as ‘kelp’ (e.g. Hay 1979; Blankley & Branch 1985; Crafford & Scholtz 1987; Marsden 1991; Beckley & Branch 1992; Hay 1994; Simpson et al. 1995; Erskine et al. 1998; Smith & Bayliss-Smith 1998; Pakhomov et al. 2002; Smith 2002; Smith & Simpson 2002; Stevens et al. 2004; Donald et al. 2005; Cainey et al. 2007; Fraser et al. 2009; Nikula et al. 2010). Similarly, in the Desmarestiales, species of Desmarestia are commonly known as ‘acid kelps’ (e.g. Johnson et al. 2008).

Figure 1  Large algal taxa that are commonly referred to as kelps occur in several phylogenetically distinct orders of brown algae (Phaeophyceae). For example, the order Fucales includes southern bull-kelp (Durvillaea) and kelp/kelpware/bladderwrack (Fucus vesiculosus); the Desmarestiales includes the acid kelps (Desmarestia); and the Laminariales includes—among others—giant bladder kelp (Macrocystis pyrifera) and strap kelp (Lessonia). The chronogram is a schematic adaptation of figure 2 from Silberfeld et al. (2010), and indicates general phylogenetic relationships and rough estimates of divergence times among phaeophyceaen orders (note: refer to Silberfeld et al. 2010 for uncertainty estimates), based on multi-gene molecular data. In the photographs, white scale bars represent approximately 40 mm, and the black bars approximately 200 mm. Photograph details: top left: Durvillaea poha (Fraser et al. in press) [C. Fraser] and top right: Durvillaea antarctica [C. Fraser]; centre left: Macrocystis pyrifera [Erasmo Macaya Horta] and centre right: Lessonia [C. Fraser]; bottom left: Desmarestia ligulata [Erasmo Macaya Horta] and bottom right: Desmarestia ligulata [C. Fraser].

Table 1  Some examples of kelp-based common names applying to brown algae from various orders. Note that some common names (e.g. ‘giant kelp’) are used for more than one taxon. This list is indicative only, and is certainly not exhaustive, either in terms of the taxa that are known as kelps, or in the lists of common names for each taxon.

Order	Genus	Species	Common name/s
Fucales	Fucus	vesiculosus	kelp; kelpware; bladderwrack
	Durvillaea		bull-kelp; southern bull-kelp
	Cystoseira	osmundacea	chainbladder kelp
	Sargassum	mangarevense	common kelp
Laminariales	Nereocystis	luetkeana	bull-kelp; edible kelp;
			ribbon kelp; giant kelp
	Macrocystis	pyrifera	giant kelp; giant bladder kelp;
			giant Pacific kelp; iodine kelp
	Lessonia		strap kelp
	Ecklonia	radiata	common kelp
Desmarestiales	Desmarestia	viridis	stringy acid kelp;
			green acid kelp
	Desmarestia	ligulata	flattened acid kelp; acid kelp

Conclusions

‘Kelp’ is used by some scientists to refer only to the Laminariales, and by others to refer to almost any large brown macroalga. Examination of the word's etymology demonstrates that the latter, broader definition is certainly valid. A possible solution to the confusion caused by such conflicting uses of the word—and one that would likely appeal to the non-specialist—would be to expand the phycological definition of ‘kelp’ to once again encompass all the large brown algae. Further definition could then, if necessary, be added with a simple adjective, e.g. ‘laminarialean’ kelp or ‘fucalean’ kelp. Placing strict rules on the use of what is essentially a common word can only exacerbate confusion and miscommunication among scientists and the general public. The role of common names in biology is not to provide a unique, unambiguous word that can apply to only one taxon, but to facilitate recognition and discussion of taxa in pre-defined contexts.

Acknowledgements

Thanks to Jon Waters, Hamish Spencer, Joe Zuccarello, Raisa Nikula, Amit Paradkar and Georgina Pickerell for comments on the manuscript. Thanks to Wendy Nelson for suggesting some source literature.

Additional information

Notes on contributors

CI Fraser

Current address: Lutte biologique et Ecologie spatiale (Biological Control and Spatial Ecology Lab), Université Libre de Bruxelles, 50 av FD Roosevelt CP 160/12, 1050 Bruxelles, Belgium