Mariculture
The distinguishing traits of onshore mariculture are the use of seawater rather than fresh, and that food and nutrients are provided by the water column, not added artificially, a great savings in cost and preservation of the species' natural diet.
Popular cultivation techniques for inshore mariculture include creating or utilizing artificial reefs,[3][4] pens, nets, and long-line arrays of floating cages moored to the bottom.
[5] As a result of simultaneous global development and evolution over time, the term "ranch" being associated typically with inshore mariculture techniques has proved problematical.
[9] Research and commercial open ocean aquaculture facilities are in operation or under development in Panama, Australia, Chile, China, France, Ireland, Italy, Japan, Mexico, and Norway.
The largest deep water open ocean farm in the world is raising cobia 12 km off the northern coast of Panama in highly exposed sites.
[10][11] There has been considerable discussion as to how mariculture of seaweeds can be conducted in the open ocean as a means to regenerate decimated fish populations by providing both habitat and the basis of a trophic pyramid for marine life.
[12] It has been proposed that natural seaweed ecosystems can be replicated in the open ocean by creating the conditions for their growth through artificial upwelling and through submerged tubing that provide substrate.
[13][14][15][16][17] The concept envisions using artificial upwelling and floating, submerged platforms as substrate to replicate natural seaweed ecosystems that provide habitat and the basis of a trophic pyramid for marine life.
[19][20][21] The idea has received substantial public attention, notably featuring as a key solution covered by Damon Gameau’s documentary 2040 and in the book Drawdown: The Most Comprehensive Plan Ever Proposed to Reverse Global Warming edited by Paul Hawken.
Uses of commercial and industrial algae cultivation include production of nutraceuticals such as omega-3 fatty acids (as algal oil)[23][24][25] or natural food colorants and dyes, food, fertilizers, bioplastics, chemical feedstock (raw material), protein-rich animal/aquaculture feed, pharmaceuticals, and algal fuel,[26] and can also be used as a means of pollution control and natural carbon sequestration.
[27] Similarly to algae cultivation, shellfish can be farmed in multiple ways in both onshore and inshore mariculture: on ropes, in bags or cages, or directly on (or within) the bottom.
[31] Fish species selected to be raised in saltwater pens do not have any additional artificial feed requirements, as they live off of the naturally occurring nutrients within the water column.
[40] In coastal fish farms, overfeeding primarily leads to increased disposition of detritus on the seafloor (potentially smothering seafloor dwelling invertebrates and altering the physical environment), while in hatcheries and land-based farms, excess food goes to waste and can potentially impact the surrounding catchment and local coastal environment.
[40][49] Furthermore, they act as buffering systems whereby they reduce coastal erosion, and improve water quality for in situ animals by processing material and ‘filtering’ sediments.
[40][49][50] In addition, nitrogen and phosphorus compounds from food and waste may lead to blooms of phytoplankton, whose subsequent degradation can drastically reduce oxygen levels.
[53] Over the course of rearing various species, the sediment on bottom of the specific body of water becomes highly metallic with influx of copper, zinc and lead that is being introduced to the area.
