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– Variation in environmental variables. a-c) Nitrate+nitrite, phosphate and ammonium concentrations for the three sampling sites. Arrows represent an upwelling event (n=3). Bars denote SE; d) Upwelling index. Arrow represents an upwelling event; e) Seawater temperature and theoretical daylength; f) Daily integrated irradiance and precipitation.
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In temperate areas, lack of nutrients during summer, particularly N, is the main limiting factor of macroalgal growth. However, Nemo lion helminthoides (Velley) Batters in northern Spain is conspicuous in the field during this time (from mid-May to late-July). Therefore, we assumed that its nutrient requirements are low enough to be sustained by tr...
Citations
... The gross growth function depends on the theoretical maximum growth rate, μ max [day −1 ], which is limited by restriction functions shown in Equation 6.5. Here, the maximum gross growth, μ max , is set to be 75% lower from September on, since shortened day length and increased water temperature is thought to induce settlement and senescence for spring and summer macroalgae (Pato et al., 2011). Equations 6.5-6.7 are taken from Martins and Marques (2001). ...
The interest in harvesting biomass from the Baltic Sea has increased in recent years. However, there is a lack of available data on macroalgae biomass and of cost-effective methods for site-specific quantification of macroalgae. In this study, macroalgae biomass has been quantified in Trelleborg and thus the nutrient reduction that could be achieved by harvesting on a regional scale. The biomass was estimated on the basis of existing inventories of macroalgae, photic zone distribution and bottom substrata. An independent model for estimating the potential of macroalgae growth was applied where factors affecting the growth of macroalgae, for example nutrients, light and temperature, were considered. The estimated summer stock of macroalgae biomass along the 58 km coastal stretch in Trelleborg amounts to 19 000 tonnes dry weight (dwt) red filamentous algae. If 10–30% of this summer stock were to be harvested, a nutrient reduction of 50–150 t of nitrogen could be achieved. The model for estimating biomass proved promising and worthy of further investigation.
... There were interannual differences in the macrophyte traits we measured (Table 1), possibly due to abiotic factors such as light, nutrients, and flow (Dodds 1991;Pato et al. 2011). In addition, the metabolism, morphology and composition of red algae change with the rapid development of the gametophyte (Sheath et al. 1979), as with aquatic vascular plants (Bowers and Stamp 1993). ...
The rapid life cycles of freshwater algae are hypothesized to suppress selection for chemical defenses against herbivores, but this notion remains untested. Investigations of chemical defenses are rare for freshwater macrophytes and absent for freshwater red algae. We used crayfish to assess the palatability of five freshwater red algae relative to a palatable green alga and a chemically defended aquatic moss. We then assessed the roles of structural, nutritional, and chemical traits in reducing palatability. Both native and non-native crayfish preferred the green alga Cladophora glomerata to four of the five red algae. Batrachospermum helminthosum, Kumanoa
holtonii, and Tuomeya americana employed activated chemical defenses that suppressed feeding by 30–60 % following damage to algal tissues. Paralemanea annulata was defended by its cartilaginous structure, while Boldia
erythrosiphon was palatable. Activated defenses are thought to reduce ecological costs by expressing potent defenses only when actually needed; thus, activation might be favored in freshwater red algae whose short-lived gametophytes must grow and reproduce rapidly over a brief growing season. The frequency of activated chemical defenses found here (three of five species) is 3–20× higher than for surveys of marine algae or aquatic vascular plants. If typical for freshwater red algae, this suggests that (1) their chemical defenses may go undetected if chemical activation is not considered and (2) herbivory has been an important selective force in the evolution of freshwater Rhodophyta. Investigations of defenses in freshwater rhodophytes contribute to among-system comparisons and provide insights into the generality of plant–herbivore interactions and their evolution.
... They are not bloom-forming species, nor associated with pollution incidents, suggesting a different ecological strategy from opportunistic algae. Previous research suggests an endogenous control of their life cycle regulated by photoperiod aimed to optimize favourable high light conditions (Pato et al., 2011). However their nutritional strategy and potential nutrient limitation while developing in the field, their responses to available nutrient sources, or their short-term nutrient storage ability remain largely unknown (but see Guo and Mathieson, 1992;Kiirikki and Blomster, 1996;Pato et al., 2011). ...
... Previous research suggests an endogenous control of their life cycle regulated by photoperiod aimed to optimize favourable high light conditions (Pato et al., 2011). However their nutritional strategy and potential nutrient limitation while developing in the field, their responses to available nutrient sources, or their short-term nutrient storage ability remain largely unknown (but see Guo and Mathieson, 1992;Kiirikki and Blomster, 1996;Pato et al., 2011). ...
... summer-annual life cycle (e.g., Dixon and Irvine, 1977), with a macroscopic phase growing fast and reproducing from mid May to early August in northern Spain, thus facing very low nutrient conditions (Pato et al., 2011). We performed 4 separate nutrient uptake experiments (ammonium, nitrate, nitrate + ammonium, and phosphate) and also assessed the effect of overcoming nutrient limitation for growth and nutrient thallus content under natural conditions by in situ adding fertilizer pellets. ...
An important life history trait of macroalgae species is the physiological ability to cope with nutrient limiting conditions, which seasonally occur in temperate coasts while other environmental factors are adequate (e.g., sufficient light). Nitrogen (N) and Phosphorus (P) uptake kinetics and field growth limitation were investigated in the perennial Bifucaria bifurcata, the opportunistic Ulva intestinalis, and the summer-annual Nemalion helminthoides from Asturian coasts (N Spain). We performed 4 nutrient uptake experiments (ammonium, nitrate, nitrate + ammonium, and phosphate) and monitored the growth and N content of field individuals in the presence/absence of artificial nutrient supply to assess potential growth limitations. B. bifurcata was not actively growing during summer thus low nutrient demands probably relied on stored pools and/or the low background nutrient levels in seawater, as generally observed for perennials. Corresponding N content and uptake rates in this species were the lowest. The opportunistic U. intestinalis showed kinetics suitable for assimilating N quickly at high external concentrations in order to fulfill the high nutrient demands that support its fast-growing strategy. This response is well adapted to seasons and sites of high nutrient loading but signs of nutrient starvation during summer (decreasing growth and N content) were found in the pristine studied area. N. helminthoides showed an intermediate response in terms of thallus N content and uptake affinity, together with an inducible activation of nitrate uptake. This response assured the uptake of transient nutrient pulses without the nutrient storage response of perennials, or the costly enzymatic machinery of opportunistics. This allows N. helminthoides to effectively exploit low background nutrient conditions interrupted by transient peaks during spring-summer, when most ephemerals found difficulties to survive and perennials suspend their active growth. P uptake did not differ greatly between species suggesting its secondary importance compared to N in the tested algae. (C) 2011 Elsevier B.V. All rights reserved.
