Effects of concurrent low temperature and low nitrogen supply on polar and temperate seaweeds

Abstract

Antarctic and arctic marine waters have simiiar near-freezing temperatures, but differ greatly in dissolved inorganic nitrogen (DIN) availabiiity. Antarctic algae have high DIN supply yearround; arctic algae are N-iimited during the Summer. Temperate algae experience low temperatures and low DIN supply on a seasonal basis, but never concurrently. Nitrogen supply iniluences the abiiity of algae to achieve the high enzyme activities necessary for cold a c c h a t i o n . The present study compared N-ailocation strategies of antarctic, arctic, and temperate seaweeds grown under N-replete and N-iimited conditions at near-freezing temperature. Sporophytes of the antarctic endemic, Himantothdus grandifolius, did not store NO3-, had small pools of nitrogenous compounds, and were unable to sustain growth for longer than 1 mo under N-iimitation. However, N-starved plants with negative growth rates exhibited chlorophyll fluorescence ratios (FJF,) simiiar to those of N-replete plants, and photosynthetic rates remained positive, suggesting that PSI1 reaction centres (RCII) were functioning efficiently. In contrast, the arctic endemic, Laminaria solidungula, maintained relatively high growth rates dunng 9 mo of N-starvation. The arctic kelp utilised both internal N O 3 p 0 0 l~ and organic nitrogenous components, such as protein and chlorophyll, to support growth. Despite declines in the density of RCII and photosynthetic capacity, N-iimited L. solidungula continued to accurnulate carbon reserves. Like the arctic plants, temperate L. saccharina from the Atlantic coast of Maine had internal reserves of NO3-and organic compounds that provided the initial N-source for growth under low external N-supply. The internal N-reserves were depleted fairly rapidly, however, and the temperate kelp showed simultaneous reductions in growth rate, photosynthetic capacity, and FJF, after only 3 mo under low N-supply. Overall, the arctic species alone has an N-aliocation strategy for surviving long penods of concurrent low temperature and low N-supply. The antarctic species appears to be primarily adapted to maintaining photosynthesis and growth under low light and low temperature, rather than low DIN supply. The temperate species is poorly adapted to survive prolonged penods of both low N and low temperature, even though ecotypes of this species extend into the Arctic.

Nitrogen load and irradiance affect morphology, photosynthesis and growth of Caulerpa prolifera (Bryopsidales: Chlorophyta)

“…This view was supported by the results of Young & Beardall (2003). Decreases in F v /F m as a result of nutrient limitation were also found in macroalgae (Henley et al 1991, Korb & Gerard 2000, Gordillo et al 2003; however, in all these studies algae were N-starved. The results from this study show that Caulerpa prolifera can maintain a high F v /F m under low, but constant, nutrient availability (nutrient limitation, Expt 1).…”

Effects of ultraviolet radiation on Laminaria saccharina in relation to depth and tidal height in the Gulf of Maine

“…We also calculated that 37 to 40% of the reaction centers are inactive in mid and deep algal populations. One explanation for this is that during the late spring and summer, when these studies were conducted, these macrophytes are nitrogen-limited; this would affect protein turnover and the number of functional PSII reaction centers (Korb & Gerard 2000).…”

Short-term effects of CO2, nutrients and temperature on three marine macroalgae under solar radiation

“…The relationship between seawater N concentrations and pigment contents in brown algae is less well documented, although under controlled conditions, pigment levels increased e.g. in Ascophyllum nodosum (Stengel & Dring 1998) and several kelp species (Korb & Gerard 2000); also several observations from field populations report on pigment changes in response to in situ nutrient levels (Henley & Dunton 1995). In line with its coarsely branched morphology and thus lower surface-to-volume ratio compared to the other species, N uptake by C. tamariscifolia (as indicated by disappearance from the media) was less pronounced than that by the other species, although both LCHN and HCHN treatments resulted in elevated chl a levels.…”