What is the difference between algae and phytoplankton

Not all blooms are visible to the naked eye. In central and northern California, many blooms are caused by natural shifts in ocean currents and wind circulation. In the spring through the early fall, a pattern of strong winds causes surface waters to move away from the shoreline, causing colder, nutrient-rich deeper water to rise. This phenomenon is known as coastal upwelling and the nutrients from the deeper water allow algae to grow and support the coastal food web.

Algae can grow to excessive numbers after an upwelling ends, winds die down and the surface waters warm and stratify. When the waters stratify, phytoplankton are trapped near the surface, forming a bloom. Other regional bloom events may be linked to overfeeding — that is, when excess nutrients like phosphorus, nitrogen and carbon from farms and lawns flow downriver to the ocean and build up at a rate that stimulates excessive algae growth beyond healthy levels.

This is called eutrophication. The vast majority of the approximately 5, known species of phytoplankton are not harmful and serve as the base of the food web. Only several dozen species — harmful algae — are known to produce toxins that can kill fish, shellfish, mammals, birds and even humans. Harmful Algal Blooms HABs produce biotoxins that can bioaccumulate in the marine food web similar to mercury. Bioaccumulation happens when toxins build up in an organism at a rate faster than they can be broken down.

Sometimes organisms are not affected by the toxins themselves, but act as vectors and transport the toxins up the food web into higher level organisms such as fish, seabirds, manatees, sea lions, turtles and dolphins. In addition to impacts of single HAB events, the effects of chronic exposure to HAB toxins on these animals can lead to changes in overall health, reproductive failure and behavior changes. Importance of phytoplankton The food web Phytoplankton are the foundation of the aquatic food web, the primary producers , feeding everything from microscopic, animal-like zooplankton to multi-ton whales.

Climate and the Carbon Cycle Through photosynthesis, phytoplankton consume carbon dioxide on a scale equivalent to forests and other land plants. Return to: Importance of phytoplankton. Studying phytoplankton Phytoplankton samples can be taken directly from the water at permanent observation stations or from ships. Global Patterns and Cycles Differences from place to place Phytoplankton thrive along coastlines and continental shelves, along the equator in the Pacific and Atlantic Oceans, and in high-latitude areas.

Differences from season to season Like plants on land, phytoplankton growth varies seasonally. Long-term changes in phytoplankton Productivity Because phytoplankton are so crucial to ocean biology and climate, any change in their productivity could have a significant influence on biodiversity, fisheries and the human food supply, and the pace of global warming. Species composition Hundreds of thousands of species of phytoplankton live in Earth's oceans, each adapted to particular water conditions.

References Behrenfeld, M. Global ocean phytoplankton. Peterson, and M. Baringer Eds. Bulletin of the American Meteorological Society.

Behrenfeld, M. Climate-driven trends in contemporary ocean productivity. Nature, , Ecology, 91 4 , Bopp, L. Response of diatoms distribution to global warming and potential implications: A global model study. Geophysical Research Letters, 32 L Carbon Cycle. Retrieved June 1, Diaz, R. Science, , Feldman, G. Science, , — Gaines, S. Background: Upwelling. Retrieved May 20, Goes, J.

Hallegraeff, G. Journal of Phycology, 46 2 , Hendiarti, N. Gregg, W. Ocean primary production and climate: Global decadal changes. Geophysical Research Letters, 30 McClain, C. Subtropical gyre variability observed by ocean-color satellites. Polovina, J. Geophysical Research Letters, 35 3. Richardson, A. Susanto, R. Geochemistry Geophysics Geosystems, 7, Q Yoder, J. Phytoplankton are typically 3 to 5 percent denser than their surrounding environment.

Consequently, most phytoplankton are constantly sinking and require turbulent mixing to stay in the upper mixed layer where light levels are appropriate for growth.

Many phytoplankton, particularly bloom-forming taxa, avoid settling losses by having either flagella that allow them to swim or ballast mechanisms that provide buoyancy [10]. Cyanobacteria are notorious for accumulating by flotation into dense surface scums Figure 2.

In a water body with constant volume, any water inputs must be accompanied by an equivalent water loss. For example, riverine water inputs to a lake are matched by outflows from the lake. If we assume that the river contains negligible phytoplankton, then river water dilutes phytoplankton densities in the lake at a rate equivalent to the river flow rate divided by lake volume.

If the dilution rate is higher than net growth rate, then the physical effect of flushing will prevent bloom development. The reciprocal of dilution rate is the water residence time which is the average amount of time that a parcel of water spends within a body of water. Generally, water bodies with residence times of a few days or less will not develop phytoplankton blooms. In water bodies with long residence times e. In addition to natural flow conditions, residence time and bloom development can be affected by water control infrastructure [11] [12] [13].

Dams and other flow manipulating structures e. Phytoplankton blooms threaten the health of aquatic organisms and the health of humans, pets, or livestock that use affected waters for drinking or recreation. High concentrations of phytoplankton during bloom conditions colors and clouds the water limiting the transmission of light in the water column. In shallow systems, light levels along the bottom may become insufficient to support beneficial submerged aquatic vegetation SAV that provide habitat, remove nutrients from the water column, and stabilize bottom sediments.

Once the SAV is gone, suspension of destabilized sediments causes an increase in turbidity, which in turn often prevents the SAV from returning. The nutrients that were previously consumed by SAV, are consumed by phytoplankton instead, further perpetuating blooms. These feedback mechanisms can trap a water body in this undesirable alternative stable state [14]. Of all the negative impacts of phytoplankton blooms, production of toxins by some bloom-forming species represents the most direct threat to human health.

Cyanobacteria and dinoflagellates are the most common toxin producing group of phytoplankton in fresh and marine waters, respectively. Cyanobacteria produce a wide variety of cyanotoxins including hepatotoxic liver-damaging microcystins, nodularins, and cylindrospermopsins, neurotoxic nerve-damaging saxitoxins and anatoxins, and dermatoxic skin-damaging lyngbya toxins [15]. Ingestion of toxins in drinking water and contact during recreation activities are the two most common exposure pathways to humans, pets and livestock.

Some dinoflagellate blooms also produce the neurotoxin saxitoxin which can bioaccumulate in shellfish and cause paralytic shellfish poisoning in humans or other shellfish eating animals. Red tide dinoflagellate blooms of the genus Karenia produce brevetoxins that kill fish and other marine life and, when aerosolized by wave action, can cause respiratory irritation in humans [17].

Habitat loss is another potential consequence of phytoplankton blooms. Although phytoplankton photosynthesis produces oxygen, the decomposition of the dead phytoplankton organic matter can deplete dissolved oxygen in the water to levels too low for fish and other animals.

The result is restricted habitat availability due to these dead zones and occasionally mass mortality events i. Hypoxia low oxygen or anoxia no oxygen is particularly common in bottom waters that are disconnected from the atmosphere by a temperature gradient thermocline in lakes or salinity gradient halocline in estuaries. Further exacerbating the problem, hypoxia increases nutrient release from sediments. Under hypoxic conditions phosphorus P is released from the sediments due to reduction of iron hydroxides that bind phosphate.

Additionally, fluxes of ammonium-nitrogen N into the water column are enhanced under hypoxic or anoxic conditions when denitrification becomes limited by a lack of nitrate [19]. Under oxic normal oxygen conditions, nitrate would be produced by nitrification of ammonium.

The increased release of N and P from the sediments under hypoxic conditions can fuel phytoplankton blooms presenting a major challenge to restoring water quality and aquatic habitats. Water bodies that are enriched with nutrients and characterized by degraded habitats are referred to as eutrophic Figure 3 [20]. Bloom mitigation strategies can broadly be grouped by those strategies that address the root causes versus those that alleviate the symptoms of an algal bloom.

Reduce External Nutrient Loading. The first step in designing nutrient controls is determining what nutrient s limit phytoplankton growth. Nitrogen N and phosphorus P have been commonly assumed to be the limiting nutrients for fresh and marine waters [2] , respectively.

However, recent studies [21] [22] have shown that the limiting nutrient can change seasonally. Once the limiting nutrients have been identified, nutrient reduction targets are generally formulated using models that relate nutrient loads to phytoplankton biomass.

Enacting watershed-based controls on nutrient sources is the best strategy for large water bodies [23]. Water Column Mixing. Artificial vertical mixing can reduce the intensity of cyanobacteria blooms through two mechanisms. First, mixing oxygenated surface waters downward reduces sediment loading of N and P that results when sediments become anoxic. Second, vigorous vertical mixing negates the floating ability of cyanobacteria which leads to lower light availability and minimizes the competitive advantage buoyant taxa have over more desirable, negatively buoyant taxa e.

Energy requirements to produce sufficiently vigorous mixing are high, and attempts to mix large water bodies with low powered mixers have been unsuccessful [25] [26]. For large water bodies, nutrient control and, where possible, prevention of long residence time conditions are the most feasible, long term solutions to bloom problems [23]. Legacy Nutrient Removal. Organic-rich sediments that result from decades of nutrient over-enrichment can continue to provide high internal nutrient loads that fuel blooms even after external sources of N and P have been reduced [23].

Application of alum or modified clay has been used successfully in small to medium sized freshwater bodies to flocculate P and phytoplankton cells out of the water column.

Once the clay has settled, it can form a cap on the sediments to prevent P from diffusing back to the water column during anoxic periods.