Productivity and nutrient relationships in psammophytic versus epilithic forms of Bryopsidales (Chlorophyta): comparisons based on a short-term physiological assay

Abstract

Members of the green algal order Bryopsidales ( = Caulerpales) are important calcifying agents of tropical reefs and comprise two fundamentally different life-form groups : (1) epilithic species with limited attachment structures and (2) psammophytic forms that have extensive subterranean rhizoidal systems . Because the shallow-water habitats of the former have relatively low nitrogen (N) to phosphorus (P;) ratios compared to the pore waters of the sedimentary carbonate-rich substrata in which the latter are anchored, we hypothesized that epilithic forms should tend to be relatively more limited by N, while psammophytic species should tend to show P ; limitation . In partial support of the hypothesis, lightsaturated net photosynthesis (PmaX) in the epilithic forms, Halimeda opuntia, H. lacrimosa and H. copiosa, tended to be enhanced by N, while P i was inhibitory or had no effect . In contrast, the psammophytic forms, Udotea sp ., U. conglutinata, H. monile, H. tuna and H. simulans, tended to be stimulated more by P;, whereas N had little effect . The utility of a bioassay to assess macroalgal nutrient limitation, based on a physiological response (net PmaX) to short-term nutrient pulses, is demonstrated .

Tissue Nutrient Content in Ulva spp. (Chlorophyceae) as Bioindicator for Nutrient Loading Along the Coast of East Africa

“…This contradicts the common assumption of P limitation in tropical areas (e.g. [48,[50][51][52][53]), especially as the present study showed the same pattern in both eutrophicated and pristine areas. N:P ratios tended to decrease along the gradients, which was mainly attributed to declines in N content, rather than increases in P content (Table 1).…”

Photosynthesis vs. irradiance curves for six species of macroalgae from the Seychelles Islands under four levels of nutrient enrichment

“…This dichotomy overlooks many siphonaceous algae (=rhizophytes), such as Udotea orientalis, prevalent in habitats characterized by sedimentary substrata. Such algae, mainly of the order Bryopsidales, anchored in nutrient-laden pore waters (Littler and Littler 1990), also have extensive root-like and rhizomatous systems for attachment in soft substrata and, because cross walls are minimal, these plants can utilize active transport, rapid turnover and cytoplasmic streaming to translocate nutrients taken up from both the sedimentary pore waters and water column milieu (Williams 1984). Udotea orientalis (Fig.…”

Guide to the dominant macroalgae of the stromatolite fringing reef complex, Highborne Cay, Bahamas

“…The myriad of algal habitats have not been intensively investigated in terms of coverage. Historical treatments in the past 75 years are limited to mostly ecologcial works and more limited floras and monographs (e.g., Jensen, 1985;Littler et al, 1985Littler et al, , 1986Littler et al, , 1988Littler et al, , 1991Littler and Littler, 1990a, 1990b, 1991, 1992, 2000, 2004Lapointe et al, 1992Lapointe et al, , 2004, in press a, in press b). Bahamian specimens and distributional records were also used to produce field guides such as Littler et al (1989) and Littler and Littler (2000).…”