Green seaweeds 'Fuzzy' seaweeds Rockweeds Kelp Irish moss Barnacles "White Rocks" 2005 Seaweed Update
Today's changing trends in seaweeds undoubtedly hold important clues as to the exact nature of the 'trouble' affecting marine life in general. The most usual interpretation of seaweed changes appears to be to attribute changes to nutrient overload, or "eutrophication," of coastal waters. (Schramm and Nienhuis, 1996) And sometimes changes are attributed to global warming. (Barry et al. 1995) But a close look, considering all species together, seems to give clearly conflicting signals...the presence in northern temperate zones of many new short-lived green seaweeds and fuzzy, filamentous types, is widely thought to have been stimulated by an INCREASING availability of dissolved nutrients in seawater. But, often growing on the same rock are examples of the previously dominant thicker, longer-lived species (kelp, rockweed, Irish moss) displaying changes that appear to have been induced by a DECREASING availability of dissolved nutrients. Which is it? In the photo at right of subtidal seaweeds at Shad Bay, N.S., tan and green 'fuzzy' growths are prevalent (due to high nutrients?) and Irish moss, rockweed and kelp all show relatively low pigmentation (due to low nutrients?). Also the green perennial Codium fragile shows prominent colorless hair development, a characteristic of this plant when grown under conditions of low nutrient availability. (Lobban and Harrison, 1994) In Atlantic Canada, this area contains far fewer fish than it did years ago, and populations of barnacles and mussels are in decline. All of these facts need to be considered together, if we hope to solve the puzzle. Correct conclusions are unlikely to be drawn based on the appearance of one seaweed species, or the abundance of one fish stock. I've grouped the seaweed photos into six galleries...but a 'single species approach' is inappropriate here, all must be considered together. A gallery of barnacles is included (although they are obviously not algae) because of their proximity, and the necessity of looking at plants and animals together when assessing the health of ecosystems. Links to galleries:
Green seaweeds Rockweeds Fuzzy seaweeds Kelp Irish moss Barnacles 2005 Seaweed Update
Barry, J. P., C. H. Baxter, R. D. Sagarin, and S. E. Gilman. 1995. Climate-related, long-term faunal changes in a California rocky intertidal community. Science 267:672-675.
Lobban, Christopher S. and Paul J. Harrison. 1994. Seaweed Ecology and Physiology. Cambridge University Press.
Schramm, Winfrid and Pieter H. Nienhuis (eds). 1996. Marine Benthic Vegetation, Recent Changes and the Effects of Eutrophication. Springer.