Globally, seafood consumption has been on the rise for over 50 years. Between 1961 and 2016, the average annual increase in worldwide seafood consumption was higher than the increases in consumption of beef, pork, and poultry combined. While seafood consumption has increased, global fishing catch – the tonnage of wild fin fish, crustaceans, molluscs, and other seafood caught each year – has remained relatively static since the late 1980s. In that time, aquaculture production has grown to meet the demand that wild fisheries could not Aquaculture is now the fastest-growing food sector and, as of 2016, provides more than half of all the seafood we eat globally. As the human population continues to grow, global demand for seafood will rise. A recent study by Hunter et al. concluded that by 2050, total food production will need to increase by as much as 70% in order to feed the projected population of 9.7 billion people. A significant portion of this increase will likely come from animal protein demanded by a growing middle class. With wild capture fisheries unlikely to meet increasing demand, aquaculture will play a critical role in feeding the world.Finfish, shellfish, and seaweed are farmed around the world both on land and in the ocean. On land, farmers primarily utilize freshwater ponds, lakes, and streams, though in some parts of the world, fully indoor, tank-based recirculating aquaculture systems are on the rise. Land-based aquaculture is often called “inland aquaculture.” In the ocean, the vast majority of seafood farming is done close to shore, in bays, estuaries, fjords, industrial drying racks and coastal waters Some marine aquaculture is done in the open ocean, sometimes miles from shore, where the water is deeper and farmers must contend with storms and higher wave energy Inland aquaculture currently contributes the vast majority of global aquaculture production and most of that is fin fish.
This farming method, particularly when it is done in ponds, lakes, and streams, must contend with other land and water uses; these conflicts will only increase as the human population grows. Non-RAS inland aquaculture can have negative environmental effects, such as pollution of freshwater drinking sources, ecosystem eutrophication, deforestation, and alteration of natural landscapes, particularly when it is done in developing countries without adequate regulation and oversight. RAS farming seeks to minimize these environmental effects by farming in indoor, closed systems – and many RAS companies market themselves as a sustainable alternative to other farming methods – but it has its own environmental trade-offs, including high energy use. RAS farming typically utilizes less land and water than traditional inland farming and will likely play a key role in future aquaculture production, particularly as the industry embraces renewable energy and technological innovation. However, with population growth increasing constraints on space and freshwater availability, the greatest potential for expanding production is in the ocean. Most marine aquaculture takes place in nearshore, coastal waters. As with inland aquaculture, these farms often compete with human uses. These conflicts can include coastal fishing grounds, recreational boating areas, and resistance from coastal landowners. Nearshore aquaculture can also negatively impact coastal ecosystems. Most notably, if they aren’t sited in areas with enough water movement, waste and excess feed can build up on the seafloor and negatively affect surrounding habitats. In some areas, nearshore farming has also resulted in modification/destruction of estuaries, mangroves, and other important coastal habitats.
Responsible, well-sited, nearshore aquaculture operations can minimize environmental impacts and can avoid use conflicts by farming in remote areas with sufficient water movement. Another option is to move operations out into the open ocean, into deeper, offshore waters where there is more space, fewer use conflicts, and strong currents to flush waste from the nets. This report will discuss the present status and future of offshore aquaculture in the United States, with a specific focus on offshore fin fish farming, which has been the subject of myriad news stories, lawsuits, industry reports, and government memoranda in recent years.Norway is the world’s second largest exporter of fish and seafood, ranking only behind China, and is the leading producer of Atlantic salmon, with 1.2 million metric tons of annual production. The Norwegian government has publicly announced its intention to increase salmon production from 1 million mt to 5 million mt by 2050 but most salmon is currently produced in nearshore coastal waters and fjords, where expansion is increasingly limited by coastal acreage and environmental concerns such as fish escapes and the prevalence of sea lice. In late 2015, the Norwegian Ministry of Fisheries and Coastal Affairs announced a program through which the government would grant free “development concessions,” i.e. experimental licenses, to projects working to develop technological solutions to the industry’s acreage and environmental challenges. The free concessions are available for up to 15 years and if the project meets a set of fixed criteria within that time, the experimental license can be converted into a commercial license for a NOK 10 million fee, significantly less than the typical NOK 50-60 million licensing fee.
Proposed projects must be large-scale and backed by teams with proven expertise in both aquaculture and offshore infrastructure, such as offshore oil and gas extraction. Each experimental license allows for up to 780mt production, so some larger projects require multiple licenses. To date, companies representing 104 individual projects have applied for 898 of these experimental licenses; 53 licenses have been granted. The ‘biological pump’, a critical component of global bio-geochemical cycles, is responsible for transporting the carbon and nitrogen fixed by phytoplankton in the euphotic zone to the deep ocean . Within the biological pump, the relative contributions of phytoplankton production, aggregation , mineral ballasting , and mesozooplankton grazing to vertical carbon flux are still hotly debated and likely to vary spatially and temporally . While solid arguments exist supporting the importance of each export mechanism, the difficulty of quantifying and comparing individual processes insitu has resulted in investigators using a variety of models, which may support one hypothesis but not exclude others. As such, experimental evidence is needed to assess the nature of sinking material, and how it varies among and within ecosystems. Mesozooplankton can mediate biogeochemicallyrelevant processes in many ways, and thus play crucial roles in global carbon and nitrogen cycles. By packaging organic matter into dense, rapidly sinking fecal pellets, mesozooplankton can efficiently transport carbon and associated nutrients out of the surface ocean on passively sinking particles . In the California Current Ecosystem , for example, Stukel et al. have suggested that fecal pellet production by mesozooplankton is sufficient to account for all of the observed variability in vertical carbon fluxes. Diel vertically migrating mesozooplankton may also actively transport carbon and nitrogen to depth when they feed at the surface at night but descend during the day to respire, excrete, and sometimes die . At times, mesozooplankton are also able to regulate carbon export rates by exerting top-down grazing pressure on phytoplankton or consuming sinking particles . In this study, we utilize sediment traps and 234Th:238U disequilibrium to determine total passive sinking flux, and paired day-night vertically-stratified net tows to quantify the contributions of mesozooplankton to active transport during 2 cruises of the CCE Long-Term Ecological Research program in April 2007 and October 2008. Using microscopic enumeration of fecal pellets we show that, across a wide range of environmental conditions, commercial greenhouse benches identifiable fecal pellets account for a mean of 35% of passive carbon export at 100 m depth, with pigment analyses suggesting that total sinking flux of fecal material may be even higher. On average, mesozooplankton active transport contributes an additional 19 mg C m−2 d−1 that is not assessed by typical carbon export measurements.Data for this study come from 2 cruises of the CCELTER program conducted during April 2007 and October 2008 . During the study, water parcels with homogeneous characteristics were identified using satellite images of sea surface temperature and chlorophyll and site surveys with a Moving Vessel Profiler . Appropriate patches for process experiments were marked with a surface drifter with holey sock drogue at 15 m and tracked in real time using Globalstar telemetry. Another similarly drogued drift array with attached sediment traps was also deployed in close proximity to collect sinking particulate matter over the 2 to 4 d duration of each experimental cycle. During each experiment, paired day-night depthstratified samples of mesozooplankton were taken with a 1 m2 , 202 µm mesh Multiple Opening and Closing Net and Environmental Sensing System at 9 depths over the upper 450 m of the water column, with the midpoint of the tow corresponding approximately to the location of the surface drifter. These samples were later enumerated by ZooScan and grouped into broad taxonomic categories and size classes for calculation of mesozooplankton active transport.
Oblique bongo tows to 210 m were also taken at mid-night and mid-day to collect organisms for determination of size-fractionated dry weights and grazing rates of the mesozooplankton community. Size-fractionated dry weights were converted to carbon biomass using the dry weight to carbon relationships of Landry et al. .VERTEX-style drifting sediment traps were deployed on the drifter at the beginning and recovered at the end of each experimental cycle. Trap arrays consisted of 4 to 12 particle interceptor traps with an inner diameter of 70 mm and aspect ratio of 8:1. To create a semistable boundary layer immediately above the trap and minimize resuspension during recovery, each PIT had a baffle on top consisting of 14 smaller tubes with 8:1 aspect ratio. The baffle tubes were tapered at the top to ensure that all particles falling within the inner dia – meter of the PIT descended into the trap. On P0704, 8 PITs were deployed at a depth of 100 m during each cycle. On P0810, 8 to 12 PITs were deployed at 100 m, and 4 to 8 PITs were deployed near the base of the euphotic zone . Before deployment, each PIT was filled with a 2.2 l slurry composed of 0.1 µm filtered seawater with an additional 50 g l−1 NaCl to create a density interface within the tube that prevented mixing with in situ water. The traps were fixed with a final concentration of 4% formaldehyde before deployment to minimize decomposition as well as consumption by mesozoo-plankton grazers . Upon recovery, the depth of the salinity interface was determined, and the overlying water was gently removed with a peristaltic pump until only 5 cm of water remained above the interface. The water was then mixed to disrupt large clumps and screened through a 300 µm Nitex filter. The remaining >300 µm non-swimmer particles were then combined with the total <300 µm sample. Samples were then split with a Folsom splitter, and subsamples were taken for C, N, C:234Th, pigment analyses, and microscopy. Typically, subsamples of ¼ of the PIT tube contents were filtered through pre-combusted GF/F filters for organic carbon and nitrogen analyses. Filters were acidified prior to combustion in a Costech 4010 elemental combustion analyzer in the SIO Analytical Facility. Entire tubes were typically filtered through QMA filters for C:234Th analyses as described above. Triplicate subsamples were filtered, extracted in 90% acetone and analyzed for chlorophyll a and phaeopigment concentrations using acidification with HCl and a Turner Designs Model 10 fluorometer . Samples for microscopic analysis were stored in dark bottles and analyzed on land as described below.Watercress is a leafy-green crop in the Brassicaceae family, consumed widely across the world for its peppery taste and known to be the most nutrient dense salad leaf . The peppery taste is the result of high concentrations of glucosinolates – phytochemicals which can be hydrolyzed to isothiocyanates upon plant tissue damage, such as chewing, known for their potent anticancer , anti-inflammatory , and antioxidant effects that are beneficial to human health. Although ITCs are the main products of digestion depending on pH, metal ions, and other epithiospecifier proteins, nitriles can also be formed through GLS break-down and they too may have chemopreventitive properties . Watercress is high value horticultural crop. A specialty leafy vegetable, with a growing area of 282 ha in the US, with 75 ha of production in California, compared to 58 ha in the UK . It is also a high-value horticultural crop in the UK, with the market value of £8.90 per kg compared to £4.97 per kg for mixed baby leaf salad bags and represents a total value of £15 million per year .