Tidepools in Southern Rhode Island, U.S.A. I. Distribution and Seasonality of Macroalgae

Abstract

Seasonality and distribution of macroalgae in eight Rhode Island tidepools were studied over a three-year period at 39 dates. Of the 35 taxa observed in the pools, 19 were found year-round, 11 of which were 'true' perennials. The highest number of total species (32) was found in June when spring and winter annuals overlapped, and the lowest number (20) appeared in October. Most species of green algae were found yearround (7 of 9), whereas most species of brown algae were annuals (7 of 12). The number of species of brown and red algae varied seasonally with the highest number of brown algae (12) in April and the highest number of red algae (13) in June and July. Changes in percentage cover in most tidepool macroalgae were associated with changes in water temperature and incident radiation. In seven pools, the dominant species (those which cumulatively occupied more than 50% cover) were Chondrus crispus and/or Hildenbrandia rubra. The dominant species in the highest pools were always green or brown algae. The greatest number of common species (each with more than 1 % average cover) appeared in the most wave-exposed pools. The two pools with the highest littorine (Littorina littorea L.) densities (> 500m" 2 ) supported the smallest number of common macroalgal species. Within each pool there appeared a marked seasonality of macroalgal communities. Seasonal changes in common species occurrence and abundance were similar to those previously reported for pools in northern New England, as was a conspicuous absence of a significant autumn flora, but macroalgal communities in this study demonstrated a greater seasonality. Rhode Island pools are thus both representative of other New England tidepools and unique in their own right.° uc on wick, Canada, differed between seasons and empha-Worldwide, macroalgal seasonality has been docu-sized the need for year-round observations in tidepool mented in the intertidal (Hehre and Mathieson 1970, studies. Macroalgal seasonality has been documented

Spatial and temporal variability of macrobenthic communities in tidepools on a rocky shore in Nova Scotia, Canada

“…Seasonal patterns of abundance of sheets and some filamentous and coarsely branched forms of macroalgae in our study contrasted with the patterns observed in 2 previous studies of tidepools in Maine (Femino & Mathieson 1980) and Rhode Island (Wolfe & Harlin 1988a), USA. We found that sheets, such as Enteromorpha intestinalis, Petalonia fascia, Scytosiphon lomentaria and Ulva lactuca, were present mostly in early summer, whereas Femino & Mathieson (1980) and Wolfe & Harlin (1988a) recorded the occurrence of U. lactuca and S. lomentaria throughout the year.…”

“…and Spongomorpha sp., in the pools throughout the year, whereas Femino & Mathieson (1980) recorded these forms only in late spring and early summer. In contrast, we found other filamentous forms, such as Ceramium rubrum and Chaetomorpha melagoniurn, mainly in late spring and summer, whereas Femino & Mathieson (1980) and Wolfe & Harlin (1988a) found that they were present throughout most of the year. We found coarsely branched forms, such as Chordaria flagelliformis, only in late summer, whereas Fernino & Mathieson (1980) found that they were present from early spring to late fall.…”

“…We found that sheets, such as Enteromorpha intestinalis, Petalonia fascia, Scytosiphon lomentaria and Ulva lactuca, were present mostly in early summer, whereas Femino & Mathieson (1980) and Wolfe & Harlin (1988a) recorded the occurrence of U. lactuca and S. lomentaria throughout the year. We found some filamentous forms, such as Cladophora sp.…”

“…Spongornorpha, fucoids and coralline algae such as Corallina) tend to be found mainly in pools located lower on the shore, whereas other forms (e.g. Enterornorpha) dominate in pools higher on the shore (Fraser 1936, Green 1971, Daniel & Boyden 1975, GossCustard et al 1979, Femino & Mathieson 1980, Dethier 1982, 1984, Sze 1982, Wolfe & Harlin 1988a, Kooistra et al 1989. Moreover, species diversity tends to decrease in pools with increasing intertidal height (Femino & Mathieson 1980, Huggett & Griffiths 1986, Wolfe & Harlin 1988b, Kooistra et al 1989.…”

Benthic assemblages of rock pools in northern Portugal: seasonal and between-pool variability

“…On the other hand, they experience greater fluctuations of physical variables, including temperature, salinity and pH, compared with subtidal habitats, with the occurrence of very harsh conditions particularly at higher levels on the shore (Metaxas and Scheibling 1993). These factors have been invoked to explain the dominance of different groups of macroalgae in pools located at different tidal levels (Dethier 1982, Wolfe and Harlin 1988a, Kooistra et al 1989, Metaxas et al 1994) and the reduction of species diversity at increasing heights (Femino and Mathieson 1980, Huggett and Griffiths 1986, Wolfe and Harlin 1988b, Kooistra et al 1989. Moreover, assemblages are highly variable between pools located at the same height on the shore Scheibling 1993, Metaxas et al 1994), probably due to combined abiotic and biological factors.…”