Each drop of water in the ocean contains life. Plankton, which is made up of algae, bacteria, protozoa and small animals is found from the equator to the poles and from the ocean surface to its darkest depths. The amount and type of plankton in a drop of water varies depending on the environmental conditions, nutrient levels, as well as a host of other factors.
Unlike temperature or salinity, plankton concentrations are not a physical parameter of water quality but a biological parameter. Plankton is one piece of the entire ocean ecosystem and it can change as a result of not only the weather but also the dynamics of the food web. Phytoplankton, made up of algae, is eaten by zooplankton, made up of small animals, and zooplankton are eaten by fish. This food chain occurs everywhere and phytoplankton is always the first step.
In order for phytoplankton to multiply and grow it must have the correct environmental conditions, this includes lots of sunlight, nutrients such as nitrogen, phosphorus and potassium, and carbon dioxide. When sunlight, carbon dioxide, and nutrients combine with suitable temperature and salinity phytoplankton can grow very rapidly. As a result if we measure phytoplankton concentrations we can also learn something about these other factors that control their growth.
In order to quantify the amount of phytoplankton or algae in water we can measure the concentration of chlorophyll-a which is a green colored pigment used by most algae to assist in photosynthesis. Chlorophyll-a concentrations directly relate to the amount of algae present in the water column. Spectroradiometer satellite technology allows us to measure the levels of chlorophyll-a from space by observing reflected light. Traditionally algae concentrations could be estimated by visually measuring the water transparency or by taking a water sample and analyzing it in a laboratory with a spectrophotometer, both options are not scalable to understanding chlorophyll-a concentrations across a wide area. Typical chlorophyll-a concentrations can vary from zero to one hundred micrograms per liter (µg/L). High concentrations of algae can be found in small bays or near rivers while low concentrations are present in the open ocean where nutrients are scarce.
Fish, shellfish, and seaweed farmers should all be interested in monitoring chlorophyll, but for different reasons. Shellfish farmers prefer locations with higher concentrations of phytoplankton since the algae is an important food source for oysters, mussels, and clams. On the other hand, seaweed competes for the same nutrients, sunlight and carbon dioxide as phytoplankton, so locations with high concentrations of chlorophyll may also have good environmental conditions for growing seaweed. Too much phytoplankton though and the competition for nutrients may leave nothing for the seaweed. Typically a fish farmer prefers lower concentrations of algae but it is not a requirement for good farming conditions. Only when algae concentrations become very high does it pose a risk to fish farmers.
Algae blooms are a dangerous aspect of phytoplankton growth that can create risks for all types of aquaculture operations. An algae bloom can be harmful in a few different ways. In some cases rapid growth of algae will quickly lead to rapid death as all of the nutrients are used up and the sun is blocked by low transparency water; this results in a massive die off, which can lead to very low oxygen levels as the dead algae is consumed by oxygen hungry bacteria. Algae blooms can also be harmful when certain toxic species of algae grow very quickly. This toxic algae can be harmful to fish and shellfish and in some cases it can be harmful to people who consume the fish or shellfish. Algae blooms often occur where two bodies of water meet, one will be cooler and nutrient rich and the other will be warm but more nutrient poor. The nutrients plus the warm temperatures can create the perfect environment for rapid algae growth. New models are being developed that will allow us to predict where harmful and beneficial algae blooms are likely to occur two weeks or one month in advance. Predicting algae blooms by monitoring chlorophyll levels along with other parameters is important to reducing farmers risks.
Chlorophyll is an important indicator to consider for all ocean farmers. It is a signal for other water quality parameters such as nutrients, dissolved oxygen, and carbon dioxide levels. It has traditionally been a difficult parameter to measure for most farmers, but Pulse makes it easy to quickly see chlorophyll levels near your farm. Fish, shellfish, and seaweed farmers can all benefit from keeping track of chlorophyll levels.
Try Pulse for free and check the chlorophyll levels near your farm by visiting www.pulse.umitron.com
You can also read our past blog post about temperature here.
