The ocean’s microscopic inhabitants shape marine ecosystems. Among these are Skeletonema, a genus of single-celled organisms that play a significant role in the health and productivity of coastal waters worldwide. Understanding this genus helps explain the complex dynamics of aquatic environments.
Meet Skeletonema
Skeletonema is a genus of diatoms, a type of phytoplankton. These organisms are characterized by unique cell walls made of silica. Skeletonema cells are cylindrical and form long, chain-like colonies. Individual cells of Skeletonema costatum, a well-known species, typically range from 8 to 12 micrometers in diameter.
The genus Skeletonema is found globally and tolerates varying salinities and temperatures. They thrive in diverse aquatic environments, including marine, brackish, and some freshwater habitats. This adaptability allows Skeletonema species to be common in coastal waters and estuaries.
The Foundation of Marine Life
Skeletonema functions as a primary producer in marine ecosystems, converting sunlight into energy through photosynthesis. Diatoms, including Skeletonema, contribute significantly to global primary production, accounting for approximately 20% of the world’s total. This activity forms the base of the marine food web.
The energy captured by Skeletonema becomes available to herbivorous zooplankton, which then serve as food for small fish. This energy transfer continues up the food chain, supporting larger marine animals. Skeletonema costatum also plays a role in the marine carbon cycle by acquiring both organic and inorganic carbon, including bicarbonate, which helps reduce ocean acidification.
When Skeletonema Blooms
Skeletonema is well-known for forming “blooms,” which are rapid increases in population density. These blooms often lead to visible water discoloration, sometimes appearing dark brown. Several environmental factors trigger these growth events.
High nutrient availability, particularly nitrate and phosphate, is a primary driver for Skeletonema blooms. For example, a study in Hongsha Bay, China, noted a significant increase in phosphate concentrations following heavy rainfall, fueling a rapid proliferation of Skeletonema costatum. Optimal water temperatures and sufficient light also promote rapid growth. Skeletonema grows across a wide range of temperatures, with optimal growth often between 14°C and 28°C, and at salinities between 20 and 30 parts per thousand (psu).
Large Skeletonema blooms can have several environmental consequences. The massive accumulation of biomass can lead to oxygen depletion in bottom waters as the diatoms die and decompose. This reduction in dissolved oxygen can disrupt marine habitats and negatively affect fish populations. Although Skeletonema is generally considered non-toxic, extremely high densities have been associated with fish deaths due to excess mucus formation in fish gills.
Monitoring and Significance for People
Monitoring Skeletonema populations is important for understanding marine ecosystem health and predicting potential impacts on human interests. Its presence and abundance can indicate changes in water quality and nutrient levels in coastal environments. Traditional methods like microscopy and cell counting are used for monitoring, though newer techniques such as quantitative PCR (qPCR) are being developed to track specific Skeletonema species and their seasonal dynamics.
Skeletonema holds practical significance in aquaculture, cultivated as a feed source for various marine organisms. It is a nutritious diet for the larvae of shellfish, fish, shrimp, and crabs due to its high levels of proteins, lipids, carbohydrates, and antioxidants. However, extensive blooms can negatively impact fisheries and coastal tourism. Discolored water can deter tourists, and severe oxygen depletion caused by blooms can lead to fish kills, affecting commercial and recreational fishing activities.