Current conventional wisdom argues that human-induced excesses in nutrient loadings to estuaries often stimulate ‘excess’ algal production leading to hypoxia, via bacterial pathways, and subsequent reduced recruitment/survival of finfish and shellfish. Why wouldn’t such elevated production stimulate more animal production, rather than less? In a three-year study of Long Island Sound, U.S.A., a multitude of variables were quantified along a west to east gradient, to address the above question via the hypothesis that different successes among planktonic species experiencing eutrophication alter planktonic food web structure away from traditional pathways to microbial loop dominated ones. Variables studied included: nutrient concentrations and ratios (i.e. NO2, NO3, NH4, DON, PON, PO4, Silicate, N/P and N/Si), phytoplankton, protozooplanktonic ciliate, zooplankton, heterotrophic nanoplankton (HNAN), photosynthetic nanoplankton (PNAN), size-fractionated chlorophyll, larval fish and bacterial concentrations and/or species composition, and bacterial growth rates (as frequency of dividing cells, FDC). Results indicated that although current nitrogen and other nutrient loadings into the estuary are much higher than past inputs (especially in western waters), the average concentration of dissolved inorganic nutrients is similar (though slightly higher) to past values. Relative proportioning among chemical species does vary from west to east, with NH4 and dissolved organic nitrogen (DON) at times more prevalent in the west, especially in bottom waters. Excess loadings of nitrogen and other nutrients into the estuary are converted to elevated biomass of both small (< 10 µm), and large (>20 µm) phytoplankton in the west. Slightly enhanced bacterial densities and growth rates shadow the elevated chlorophyll levels, with distinctive Sound-wide seasonal patterns that follow not total chlorophyll, but rather PNAN concentrations. HNAN concentrations also are elevated in the west, and likely influence bacterial dynamics. Species composition of phytoplankton routinely differ west to east. Inorganic N/P are routinely low (i.e. below Redfield ratios), especially in the west, while total dissolved N/P (i.e. including DON) are similar among stations and typically are significantly higher than Redfield ratios. Associated with bacterial and <10 µm chlorophyll enhancements to an elevated diversity of ciliate species in the west. Copepod biomass is extremely enhanced in the west, indicating that while stimulating the microbial loop, eutrophication is also enhancing the secondary production preferred by larval fish and gelatinous zooplankton. Larval fish diversity is down relative to the past, but shows little contemporaneous west/east variations. So, if adult fish populations are down, but larvae are not food limited, possibly toxicity, overfishing, and/or habitat destruction which prevent a healthy, normal system response to eutrophication are culpable. It is suggested that recipients of the excess copepod production are likely gelatinous zooplankton and benthic sediments, and that unused copepod ‘excess’ biomass likely significantly contributes to hypoxia. New conventional wisdom: Excess nitrogen stimulates microbial loop and net phytoplankton biomass and production, which in turn stimulates microcrustasean biomass and production and fecal release, and both significantly fuel hypoxia and likely stimulate gelatinous zooplankton production.
Digital library
-
-
Government regulatory policies and social acceptance are critically important to the growth of marine aquaculture in the United States. In much of the country, opposition to marine aquaculture by local and national interest groups and local, state, tribal, or national policies have limited marine aquaculture to a scale far below its potential. There are several reason for this: (1) Marine aquaculture is relatively small, diverse, and (with some notable exceptions) unproven; (2) marine waters are public resources; (3) some Americans perceive potential negative effects of marine aquaculture without offsetting positive effects; (4) aquaculture faces significant social opposition; and (5) the governance system for leasing and regulation hinders the development of U.S. marine aquaculture. This article discusses five broad strategies and recent efforts to advance marine aquaculture in the United States: (1) fixing problems, (2) creating benefits, (3) building partnerships, (4) arguing effectively, and (5) reforming governance.
-
Enteric methane emissions from ruminant animals raised for meat and milk are a significant contributor across the globe to anthropogenic climate change. Early studies suggest seaweeds offer a promising, natural approach to enteric methane mitigation. In terms of suitability for animal consumption, numerous anecdotal observations exist from different parts of the world of cows and sheep grazing on seaweed along the shoreline. However, to date limited science has emerged that conclusively demonstrates the effect of seaweed as feed, or as a feed ingredient, on animal health and well-being.
For beef and dairy farmers, it is critically important to maintain or improve animal health, performance and productivity. While feeding seaweed to cows and other ruminants may help curb methane outputs, no farmer will use seaweed as a feed ingredient if the product adversely impacts animals. As a developing area of science, many questions must be asked and answered before it is determined that seaweed-based ingredients are effective, safe, profitable, and sustainable along every step of the value chain, from ocean to farm to human consumption.
Promising new developments, combined with broad interest in this emerging area of science, prompted the need for in-depth discussions into the potential for seaweed supplements to both mitigate enteric methane and improve livestock production. Moreover, an important paper has emerged, Key Considerations for the Use of Seaweed to Reduce Enteric Methane Emissions From Cattle, which takes a comprehensive look at the issue and will be a key benchmark for work ahead.
-
The oceans cover 70% of Earth yet they yield only 1.5% (117 million metric tons (mt)) of the 7.6 billion mt of food that we produce each year. Can we make more productive use of them? If so, how and, in light of challenges now faced by global agriculture, should we try? This paper addresses these questions by looking at seaweed farming and the idea that a parallel, photosynthetically driven system of food production, a 'Marine Agronomy', could be developed at sea to supplement the food we grow on land.
-
Integrated multi-trophic aquaculture (IMTA) has the potential of reducing open-cage fish farming impacts on the environment while also introducing new value chains. The aim of this study was to investigate the growth and composition of the kelp Saccharina latissima in salmon-driven IMTA, and to assess the spatial extent of the influence of salmon derived nitrogen in order to evaluate the upscaling potential for IMTA. S. latissima was cultivated 100, 200, and 1,000 m east and 1,000 m west of a 5,000 tons salmon farm in Western Norway from February to September 2013. The proportion of salmon derived nitrogen available for the kelp showed a clear decline with distance from the farm. Accordingly, the kelp cultivated near the salmon cages grew faster during the spring season, and growth rate decreased with increasing distance from the farm. A spatially explicit numerical model system (SINMOD), including compartments for dissolved nutrients and kelp growth, was tuned to the field data and used to investigate the potential for upscaling IMTA production. The model was used to introduce a new metric—the impacted area IA—for the areal effects of IMTA in terms of the increase in production by IMTA. The model showed that a 25 hectare kelp farm in the vicinity of the studied salmon farm could take up 1.6 of the 13.5 tons of dissolved inorganic nitrogen released during kelp cultivation, amounting to almost 12% of the ammonia released during the cultivation period from February to June. The 25 hectare kelp farm would have a production yield of 1,125 tons fresh weight (FW), being 60% more than that of a non-IMTA kelp farm, while a 20% increase of kelp FW could be obtained over a 110 hectar area in salmon-driven IMTA. To achieve an even mass balance, an area of approximately 220 ha−1 would be needed to cultivate enough kelp to fix an equivalent of the nitrogen released by the fish.
-
The production of methane biofuel from seaweeds is limited by the hydrolysis of polysaccharides. Therumen microbiota of seaweed-eating North Ronald-say sheep was studied for polysaccharidic bacterial isolates degrading brown-seaweed polysaccharides. Only nine isolates out of 65 utilized >90% of the polysaccharide they were isolated on. The nine isolates (eight Prevotellaspp. and one Clostridiumbutyricum) utilized whole Laminaria hyperborea extract and a range of seaweed polysaccharides, including alginate (seven out of nine isolates), laminarin and carboxymethylcellulose (eight out of nineisolates); while two out of nine isolates additionally hydrolysed fucoidan to some extent. Crude enzyme extracts from three of the isolates studied further had diverse glycosidases and polysaccharidase activities; particularly against laminarin and alginate (two isolates were shown to have alginate lyase activity) and notably fucoidan and carageenan (one isolate). Inserial culture rumen microbiota hydrolysed a range of seaweed polysaccharides (fucoidan to a notably lesser degree) and homogenates of L. hyperborea, mixed Fucusspp. and Ascophyllum nodosum to produce methane and acetate. The rumen microbiota and isolates represent potential adjunct organismsor enzymes which may improve hydrolysis ofseaweed components and thus improve the efficiencyof seaweed anaerobic digestion for methane biofuel production.
-
The extensive grazing systems across northern Australia support approximately 50 % of the national beef herd. Livestock productivity is affected by seasonal variation in pasture quality and quantity. Intensifying livestock production in the north is a challenge, but has been recognised as priority for the Australian economy. Macroalgae offer a sustainable and novel dietary supplement for cattle due to its high nutrient value and biomass production, which are generally superior to forages used in ruminant production systems. This paper highlights some of the existing literature associated with the use of macroalgae for beef cattle and discusses the potential of green freshwater (Cladophora vagabunda, Oedogonium sp., Spirogyra sp.) and marine macroalgae (Cladophora coelothrix, Derbesia tenuissima, Ulva ohnoi) as feed supplements in northern Australian livestock production systems. Crude protein content of the six species of green macroalgae discussed here ranged from 75.4 to 339.1 g kg−1 dry weight (DW). Dietary mineral limitations in northern livestock production systems include phosphorous (P), sulfur (S) and nitrogen. Four of the six macroalgae species had high P content, ranging from 1.4 to 5 g kg−1 DW. Sulfur varied between species, ranging from 2.9 to 57.5 g kg−1 DW, with marine macroalgae having a higher sulfur concentration than freshwater macroalgae. This review demonstrates that green macroalgae have considerable potential to supply a high-protein, high-phosphorous feed supplement for northern livestock production systems dependent on extensive unimproved pastures.
-
The food and feed industry surpass their sustainable boundaries and global food security is one of society's biggest challenges today. Macroalgae of the genus Ulva have been identified as a suitable candidate for cultivation, with various applications within the food and feed industry. This work discusses the sustainability performance of Ulva cultivation and identifies the potential of Ulva species in southern Portugal for their use in the food and feed industry. It was tested, which species are available in different coastal and lagoon habitats and whether species identity or environmental conditions have a stronger effect on the seaweed’s protein content and fatty acid profile, to find out, whether the selection of one Ulva species is favorable over another for cultivation. Ulva species were collected at coastal and lagoon locations in southern Portugal and genetically identified, using the tufA gene sequences. Ulva rigida, Ulva flexuosa, Ulva fasciata, Ulva australis and Ulva compressa were identified as potential cultivation candidates. U. australis has not previously been reported in southern Portugal. Protein content in U. rigida sampled in coastal locations was higher (p < 0.01) compared to lagoon locations, but not different among species within the Ria Formosa (p = 0.363). Fatty acid profiles were not different across locations (p = 0.739). However, U. compressa had a higher PUFA content than U. rigida and U. fasciata within the Ria Formosa (p = 0.0245). Results suggest that U. compressa might be more a more suitable Ulva candidate for PUFA production and that protein content in seaweeds may be more susceptible to environmental conditions. In southern Portugal, Ulva is still an underexploited resource but has the potential to be part of the solution to overcome food security challenges in the future.
-
This study is the first to evaluate the effects of five seaweeds (Ulva sp., Laminaria ochroleuca, Saccharina latissima, Gigartina sp., and Gracilaria vermiculophylla) on gas and methane production and ruminal fermentation parameters when incubated in vitro with two substrates (meadow hay and corn silage) for 24 h. Seaweeds led to lower gas production, with Gigartina sp. presenting the lowest value. When incubated with meadow hay, Ulva sp., Gigartina sp. and G. vermiculophylla decreased methane production, but with corn silage, methane production was only decreased by G. vermiculophylla. With meadow hay, L. ochroleuca and S. latissima promoted similar methane production as the control, but with corn silage, L. ochroleuca increased it. With the exception of S. latissima, all seaweeds promoted similar levels of total volatile fatty acid production. The highest proportion of acetic acid was produced with Ulva sp., G. vermiculophylla, and S. latissima; the highest proportion of butyric acid with the control and L. ochroleuca; and the highest proportion of iso-valeric acid with Gigartina sp. These results reveal the potential of seaweeds to mitigate ruminal methane production and the importance of the basal diet. To efficiently use seaweeds as feed ingredients with nutritional and environmental benefits, more research is required to determine the mechanisms underlying seaweed and substrate interactions.
-
As Tornabene1,2 has already discussed in this and in an earlier volume, many microorganisms — photosynthetic or not — are capable of producing hydrocarbons which can account for up to 1% of the dry mass (see tables I–V in ref. 1). At the moment, it seems that there is only 1 exception described in the literature which produces a larger proportion: the unicellular green alga Botryococcus braunii.
Pages
Marine Agronomy Group, CAFNRM, UH-Hilo
200 W. Kawili st., HI 96720, USA
Contact: Marine.Agronomy.Group@gmail.com
Funding for this web portal is provided by the World Wildlife Fund and the University of Hawaii-Hilo.