Aquaculture is the farming and husbandry of freshwater and marine animals and plants in controlled environments. Although aquaculture serves many purposes, the most important one is to supply food for humans. It also supports the food chain at a lower level by producing algae and other plant organisms for animal feed.

List of Pros of Aquaculture

1. Source of Food for People and Marine Species: an effective solution to meet the increasing demand for seafood and other fish species.

2. Source of Income: this gives livelihood to fishermen and other people since it opens job opportunities.

3. Flexibility: fish farms can be built and established anywhere where there is body of water.

4. Helps Waste Problems: re-circulating aquaculture systems is also a big help in reducing, reusing and recycling waste materials that is healthy not only for the cultured species of fish but also to the environment.

List of Cons of Aquaculture

1. Propagation of Invasive Species: it can lead to the increase population of invasive species that are harmful to the other marine species because they take away the food supply for fishes in the wild.

2. Threat to Coastal Ecosystems: this method does not help in recycling wastes but instead cause it.

3. Contaminates Water and Threatens Health: since fish farms can be built basically in any body of water, the chances for water contamination are higher since waste products from the fish can stay in the water which is sometimes used for drinking by people in poor communities.

4. Affects Wild Fish Population: it takes more than just an ample amount of wild fish to feed one salmon for commercial consumption. This can result to diminished supply of wild fish that can affect the population as well as the continuity of marine life.

5. Impact on the Environment: the changes in the habitat that need to be made to build fish cages and tanks could result in destruction of properties and loss of lives can happen during cyclones and hurricanes.

Types of aquaculture

Mariculture: cultivates marine organisms either in the open ocean, an enclosed portion of the ocean, or tanks or ponds filled with seawater. Finfish (like flounder and whiting), shellfish (like prawns and oysters), and sea plants (like kelp and seaweed) are cultured in saltwater.

Algaculture: cultivates algae. Most algae harvested is either microalgae (phytoplankton, microphytes or planktonic algae) or macroalgae, commonly known as seaweed. Its size and cultivation needs make it hard to grow. Microalgae are easier to harvest on a large scale.

Integrated multitrophic aquaculture: (IMTA) is a more advanced system of aquaculture. In a multitrophic system, different species with various nutritional needs are combined into one system. 

Factors when choosing potential new aquatic organisms

• reproductive habits

• requirements of eggs and larvae

• adaptability to crowded conditions

• feeding habits of organisms

Issues

1. Living conditions

2. Potential diseases affecting aquatic organisms

3. Aquaculture's impact on the environment

4. Animal cruelty

Aquacultural plant production

the plants are grown mainly with two different methods: ‘Hydroponics’ is where the cultivated plants are grown with plant roots directly exposed to water; and ‘Floating Plant Ponds. A floating plant pond is a modified maturation pond with floating (macrophyte) plants. Plants such as water hyacinths or duckweed float on the surface while the roots hang down into the water to uptake nutrients and filter the water that flows by. 

Hydroponics

Plants are grown in a liquid solution consisting of water and the required nutrients of a particular plant, or within a system that uses a substrate or growing mix medium in addition to the liquid (water) nutrient flow.

The required nutrients are determined based on the plant needs and mixed into a plant's water supply artificially. Nutrient-rich wastewater flowstreams such as urine, reclaimed water from wastewater treatment plants, pretreated greywater or water coming from fish production ponds can be used as a source of water and nutrients.

Hydroponic systems are used to produce, tomatoes, lettuce, watercress, chinese cabbages, bock choy, shoots of plants including beans, and barley, and varieties of flowers and even tree seedlings are grown using hydroponics.

Requirements

• A sufficient amount of land (or pre-existing pond)

• Warm or tropical climates with no freezing temperatures, and preferably with high rainfall and minimal evaporation.

• Trained staff is required for the constant operation and maintenance of the pond.

• The fish and plants should have similar needs as far as temperature and pH. (As a general rule, warm, fresh water, fish and leafy crops such as lettuce and herbs will do the best. In a system heavily stocked with fish, you may have luck with fruiting plants such as tomatoes and peppers.)

Plants that will do well in any aquaponic system:

• any leafy lettuce

• pak choi

• kale

• swiss chard

• arugula

• basil

• mint

• watercress

• chives

• most common house plants

Plants that have higher nutritional demands and will only do well in a heavily stocked, well established aquaponic system:

• tomatoes

• peppers

• cucumbers

• beans

• peas

• squash

• broccoli

• cauliflower

• cabbage

Other crops grown in aquaponics:

• bananas

• dwarf citrus trees: lemons, limes and oranges

• dwarf pomegranate tree

• sweet corn

• micro greens

• beets

• radishes

• carrots

• onions

• edible flowers: nasturtium, violas, orchids

Algae

Algae are a diverse group of aquatic organisms that have the ability to conduct photosynthesis. They can exist as single, microscopic cells; they can be macroscopic and multicellular; live in colonies; or take on a leafy appearance as in the case of seaweeds such as giant kelp. Lastly, algae are found in a range of aquatic habitats, both freshwater and saltwater.

the general term "algae" includes prokaryotic organisms — cyanobacteria, also known as blue-green algae — as well as eukaryotic organisms (all other algal species)

Algal biofuels are a promising replacement for fossil fuels. All algae have the ability to produce energy-rich oils and several microalgal species naturally accumulate high levels of oil in their dry mass. Moreover, algae are found in diverse habitats and can reproduce quickly. They also efficiently use carbon dioxide. Green algae, diatoms and cyanobacteria are just some of the microalgal species that are considered good candidates for the production of biofuel (Biofuels, 2010). 

Algae as food

IWi is betting their strain, nannochloropsis, will be next big food trend. The company already sells algae as omega-3 and EPA supplements at the The Vitamin Shoppe and on Amazon. It's now developing algae-based snacks and protein powders.

"Algae is going to be part of a regular food chain for us. It's going to be great thing for all of us and for our planet."

IWi's strain of algae takes saltwater, desert land and CO2 and turns it into something special, made up of 40% protein, it can produce about seven times the amount of protein as soybeans on the same amount of land. The plant also releases oxygen into the air. (About 50% of the world's oxygen comes from algae).

To successfully harvest algae, an algae farm needs:

1. the right temperature range

2. light source

3. nutritional characteristics in the water source.

Algae is most commonly cultivated in open-pond systems, such as ponds, pools and lakes. However, these systems don't allow for control of light or temperature.

Closed-pond systems are pools or ponds that are covered. Even though the closed-pond system allows more species to grow, it tends to be smaller in scale, so it produces a smaller crop. One variation of the closed-pond system is the photobioreactor, a system that incorporates a light source. Although nutrients must be brought into this type of system, it can produce high-yield crops.

IWi uses an open method by harnessing the power of the sun to feed its algae. Algae at the farm is grown in long ponds called "raceways," and an engine constantly churns water to make sure the algae is exposed to the sunlight. CO2 and a tiny bit of fertilizer is then pumped into the water to help the algae bloom.

Sources:

https://animals.howstuffworks.com/animal-facts/aquaculture.htm

https://sswm.info/sswm-university-course/module-6-disaster-situations-planning-and-preparedness/further-resources/aquaculture-%28plants%29

https://aquaponics.com/recommended-plants-and-fish-in-aquaponics/https://www.livescience.com/54979-what-are-algae.html
https://money.cnn.com/2018/06/01/technology/algae-food/index.html