George P. Kraemer

Integrating seaweeds into marine aquaculture systems: a key toward sustainability

The rapid development of intensive fed aquaculture (e.g. finfish and shrimp) throughout the world is associated with concerns about the environmental impacts of such often monospecific practices, especially where activities are highly geographically concentrated or located in suboptimal sites whose assimilative capacity is poorly understood and, consequently, prone to being exceeded. One of the main environmental issues is the direct discharge of significant nutrient loads into coastal waters from open‐water systems and with the effluents from land‐based systems. In its search for best management practices, the aquaculture industry should develop innovative and responsible practices that optimize its efficiency and create diversification, while ensuring the remediation of the consequences of its activities to maintain the health of coastal waters. To avoid pronounced shifts in coastal processes, conversion, not dilution, is a common‐sense solution, used for centuries in Asian countries. By integrating fed aquaculture (finfish, shrimp) with inorganic and organic extractive aquaculture (seaweed and shellfish), the wastes of one resource user become a resource (fertilizer or food) for the others. Such a balanced ecosystem approach provides nutrient bioremediation capability, mutual benefits to the cocultured organisms, economic diversification by producing other value‐added marine crops, and increased profitability per cultivation unit for the aquaculture industry. Moreover, as guidelines and regulations on aquaculture effluents are forthcoming in several countries, using appropriately selected seaweeds as renewable biological nutrient scrubbers represents a cost‐effective means for reaching compliance by reducing the internalization of the total environmental costs. By adopting integrated polytrophic practices, the aquaculture industry should find increasing environmental, economic, and social acceptability and become a full and sustainable partner within the development of integrated coastal management frameworks.

Application of seaweed cultivation to the bioremediation of nutrient-rich effluent

A seaweed biofilter/production system of being developed to reduce the environmental impact of marine fish farm effluent in coastal ecosystems as a part of an integrated aquaculture system. Several known seaweed taxa and their cultivars have been considered as candidate biofilter organisms based on their species-specific physiological properties such as nutrient uptake kinetics and their economic value. Porphyra is an excellent cadidate and shows efficient nutrient extraction properties. Rates of ammonium uptake were maintained at around 3 at 150 inorganic nitrogen at . Ulva is another possible biofilter candidate with an uptake rate of 1.9 under same conditions. A simple uptake/growth and harvest model was applied to estimate the efficiency of the biofilter/production system. The model was deterministic and used a compartment model structure based on difference equations. The efficiency of Porpyra filter was estimated over 17% of removal from the contimuous supply of 100 flow rate.

Evaluation of the bioremediatory potential of several species of the red alga Porphyra using short-term measurements of nitrogen uptake as a rapid bioassay

Rates of inorganic nitrogen uptake by three Northeast US and three Asian species of Porphyra were compared in short-term incubations to evaluate potential for longer term and larger scale examination of bioremediation of nutrient-loaded effluents from finfish aquaculture facilities. The effects of nitrogen (N) species and concentration, temperature, acclimation history, and irradiance were investigated. Uptake rates increased ca. nine-fold from 20 to 150 μM N. Nitrate and ammonium uptake occurred at similar rates. Irradiance had a strong effect, with uptake at 40 μmol photons m−2 s−1only 55% of uptake at 150 μmol photons m−2 s−1. N-replete tissue took up inorganic nitrogen at rates that averaged only 60% of nutrient-deprived tissue. Although there were species (P. amplissima > (P. purpurea = P. umbilicalis)) and temperature effects (10 °C>5 °C>15 °C), interactions among factors indicated that individual species be considered separately. Overall, P. amplissima was the best Northeast US candidate. It took up ammonium at faster rates than other local species at 10 and 15 °C, two temperatures that fall within the expected range of industrial conditions for finfish operations.

Bait worm packaging as a potential vector of invasive species

Invasive species have become an increasingly greater concern for the ecological health of coastal ecosystems, yet vectors of these introductions often are unclear. This project evaluated the potential for the brown seaweed Ascophyllum nodosum ecad scorpiodes (Hauck) Reinke, packaged with bait worms (Nereisvirens) harvested from the coast of Maine (USA), as a vector of invasive marine fauna and flora. Often, the seaweed and contents of the bait boxes are discarded into the water by recreational fishermen after using the bait worms, and any included non-native species may then be introduced. Bait boxes were purchased from several commercial vendors in Connecticut and New York over a two-year period. Subsamples of the seaweed were placed in laboratory culture and the growth of associated macro- and microalgae was monitored. Marine invertebrate species present in the samples were also identified and quantified. Results indicated 13 species of macroalgae and 23 species of invertebrates were associated with baitboxes. Among the highly diverse microbial assemblage detected, two species of potentially toxic marine microalgae, Alexandrium fundyense Balech and Pseudonitzschia multiseries (Hasle) Hasle, were found both prior to and after incubation at various temperatures, indicating these harmful algae are brought to and can survive in receiving waters. These findings highlight the need to consider alternative choices of bait box packaging materials or appropriate disposal methods of the seaweed in order to minimize the transport of species which are not native to the receiving coastal waters.

Nitrogen uptake by gametophytes of Porphyra dioica (Bangiales, Rhodophyta) under controlled-culture conditions

Aspects of the nutrient-uptake physiology of Porphyra dioica (Brodie et Irvine) from Porto, Portugal were investigated under laboratory conditions. The capacity for uptake and accumulation of nitrogen (N) by P. dioica was determined for two different N sources, ammonium and nitrate ( ). The influence of the light–dark cycle and of the simultaneous presence of and , as well as the effects of phosphorus (P) enrichment, on the growth, nutrient uptake, and accumulation were also evaluated. Porphyra dioica was able to take up, accumulate, and grow equally well using both sources of nitrogen when presented separately. The photosynthetic pigment levels increased significantly with the increase of the availability of N, for both sources. The chlorophyll a content was higher in thalli that used as source of N, while this difference was not seen for phycobiliprotein content. When both N sources were available (NO3 : NH4 = 6 : 1), P. dioica preferentially removed , with a clear diurnal difference. During the light period, the algae removed 70% of the available, while only 35% was removed during the dark period. Phosphorus enrichment did not influence the growth rate or the amount of P removed from the medium, suggesting a limited capacity to store P. These results indicate that P. dioica is a good candidate for application in an integrated multi-trophic aquaculture (IMTA) system.

Emersion Induces Nitrogen Release and Alteration of Nitrogen Metabolism in the Intertidal Genus Porphyra

We investigated emersion-induced nitrogen (N) release from Porphyra umbilicalis Kütz. Thallus N concentration decreased during 4 h of emersion. Tissue N and soluble protein contents of P. umbilicalis were positively correlated and decreased during emersion. Growth of P. umbilicalis did not simply dilute the pre-emersion tissue N concentration. Rather, N was lost from tissues during emersion. We hypothesize that emersion-induced N release occurs when proteins are catabolized. While the δ15N value of tissues exposed to emersion was higher than that of continuously submerged tissues, further discrimination of stable N isotopes did not occur during the 4 h emersion. We conclude that N release from Porphyra during emersion did not result from bacterial denitrification, but possibly as a consequence of photorespiration. The release of N by P. umbilicalis into the environment during emersion suggests a novel role of intertidal seaweeds in the global N cycle. Emersion also altered the physiological function (nitrate uptake, nitrate reductase and glutamine synthetase activity, growth rate) of P. umbilicalis and the co-occurring upper intertidal species P. linearis Grev., though in a seasonally influenced manner. Individuals of the year round perennial species P. umbilicalis were more tolerant of emersion than ephemeral, cold temperate P. linearis in early winter. However, the mid-winter populations of both P. linearis and P. umbilicalis, had similar temporal physiological patterns during emersion.

Comparison of growth and nitrate uptake by New England Porphyra species from different tidal elevations in relation to desiccation

Desiccation stress can determine the upper distribution limits and may enhance the uptake of nitrate and ammonium of eulittoral algal species. Upper shore species may exhibit greater stimulation of nitrate uptake following desiccation and achieve maximum uptake at higher desiccation levels. The objective of this study was to determine whether Porphyra species from different vertical elevations respond differently to the desiccation stress, in terms of growth and nitrate uptake. A eulittoral species (Porphyra umbilicalis) and a sublittoral species (P. amplissima) were compared in the present study. Samples were exposed to air for 0, 30 min (40 ± 10% water loss) and 2 h (90 ± 5% water loss), after an initial 4 h light period every day. Desiccation was more stressful to the sublittoral species, Porphyra amplissima, than to the eulittoral species, P. umbilicalis. When tissues were exposed for 2 h daily, P. amplissima lost weight over a 24 h day, while the growth rate of P. umbilicalis dropped by only 30% compared with that of continuously submerged blades. Nitrate uptake rate of sublittoral P. amplissima was only 73% (40 ± 10% water loss) and 62% (90 ± 5% water loss) of that of continuously submerged tissue. Nitrate uptake rates of P. umbilicalis were not significantly affected by desiccation. These results suggest that species in the eulittoral zone, which have longer exposure times, have a higher time‐use efficiency than the sublittoral species in terms of nitrate uptake. This indicates a possible correlation between nitrate uptake and observed vertical distribution patterns.

A preliminary comparison of the mariculture potential of Porphyra purpurea and Porphyra umbilicalis

Due to their rapid growth and nutrient assimilation,Porphyra spp. are good candidates for bioremediation and polyculture. The production potential of two strains of P. purpurea and P. umbilicalis from north-east USA was evaluated by measuring rates of photosynthesis (as O2evolution) of material grown at 20 °C. Photosynthetic rates of P. umbilicalis were 80%higher than P. purpurea over the temperature range 5–20 °C, at both sub-saturating andsaturating irradiances (37 and 289 μmol photonm-2 s-1). Porphyra umbilicalis was more efficient at low irradiances (higher α) and had a higher Pmax (23.0 vs 15.6 μmolO2 g-1 DW min-1) than P.purpurea, suggesting that P. umbilicalis is a better choice for mass culture, where self-shading maybe severe.

Metabolic plasticity of nitrogen assimilation by Porphyra umbilicalis (Linnaeus) Kützing

The physical stresses associated with emersion have long been considered major factors determining the vertical zonation of intertidal seaweeds. We examined Porphyra umbilicalis (Linnaeus) Kützing thalli from the vertical extremes in elevation of an intertidal population (i.e. upper and lower intertidal zones) to determine whether Porphyra thalli acclimate to different vertical elevations on the shore with different patterns of nitrate uptake and nitrate reductase (NR) and glutamine synthetase (GS) activities in response to different degrees of emersion stress. We found that the nitrate uptake and NR recovery in the emersed tissues took longer in lower intertidal sub-population than in upper intertidal sub-population; and GS activity was also significantly affected by emersion and, interestingly, such an activity was enhanced by emersion of thalli from both upper and lower intertidal zones. These results suggested that intra-population variability in post-emersion recovery of physiological functions such as nutrient uptake and NR activity enables local adaptation and contributes to the wide vertical distribution of P. umbilicalis. The high GS activity during periodic emersion stress may be a protective mechanism enabling P. umbilicalis to assimilate nitrogen quickly when it again becomes available, and may also be an evidence of photorespiration during emersion.

Life history interactions between the red algae Chondrus crispus (Gigartinales) and Grateloupia turuturu (Halymeniales) in a changing global environment

Abstract: The invasive rhodophyte Grateloupia turuturu is a large perennial alga, discovered first in Narragansett Bay (Rhode Island) in 1994 and subsequently in the Long Island Sound estuary. The algas low intertidal to shallow subtidal distribution overlaps that of the native Chondrus crispus. Our field measurements suggest that physical disturbance may promote increased substrate cover by G. turuturu. Molecular quantification of spore abundance suggests G. turuturu produces fewer spores, which also disperse shorter distances than spores of C. crispus. However, sporelings of G. turuturu grew faster than those of C. crispus at all environmentally relevant light levels, salinities and temperatures tested. In addition, the temperature tolerance of G. turuturu sporelings was broader; C. crispus sporelings died just after germination at 30°C; whereas, those of G. turuturu survived. The results have implications for community shifts as coastal waters continue to warm into the future.