Frequently Asked Questions
To promote a productive fishery you need beneficial phytoplankton as a feed for minnow, fish fry, zooplankton, copepods and other organisms that support the food chain of the aquatic ecosystem.
Phytoplankton serves as the cornerstone of freshwater ecosystems, providing the essential first link in the aquatic food chain. These microscopic algae convert sunlight and nutrients into energy, creating a vital food source that supports zooplankton, which in turn nourishes fish larvae and fry during their most vulnerable developmental stages.
For many native fish species, the transition from egg to fry represents one of the most critical periods of life. After hatching, fish larvae depend on their yolk sac for initial nutrition. But before this supply is depleted, they must begin foraging independently—and this is where phytoplankton becomes indispensable.
Native Minnows That Depend on Phytoplankton
Several species of minnows native to the United States rely heavily on phytoplankton-based food webs during their development:
Fathead Minnows (Pimephales promelas)
Found throughout much of North America, fathead minnows are remarkably adaptable fish that play a crucial role in freshwater ecosystems. These fish can consume phytoplankton when other food sources are scarce, making them resilient survivors in varying water conditions. Young fathead minnows rely on the zooplankton that feed on phytoplankton, creating a direct nutritional link to beneficial algae populations.
Golden Shiners (Notemigonus crysoleucas)
Golden shiners are among the most widespread minnows in North America. These common minnows can filter-feed on phytoplankton when it's abundant, especially during algal blooms. Their specialized gill rakers allow them to efficiently harvest microscopic food particles from the water column, making phytoplankton an important supplementary food source throughout their lives.
Gizzard Shad (Dorosoma cepedianum)
While gizzard shad grow quite large as adults, their early life stages tell a different story. These native North American fish begin life feeding primarily on phytoplankton before transitioning to larger prey as they mature. This makes healthy phytoplankton populations absolutely critical for successful gizzard shad reproduction and recruitment.
The Critical First Feeding Stage
For fish fry across numerous species, the "first feeding" stage represents a make-or-break moment. When larvae deplete their yolk reserves and must begin feeding independently, they face a significant challenge: their digestive systems are underdeveloped, their swimming abilities are limited, and they require appropriately sized prey items.
This is where the phytoplankton-zooplankton connection becomes vital. Phytoplankton supports populations of tiny zooplankton like rotifers, copepod nauplii, and cladocerans (including daphnia and moina). These microscopic animals represent the perfect first food for newly hatched fish fry—they're the right size, slow-moving enough for inexperienced larvae to catch, and packed with essential nutrients.
How Phytoplankton Supports Fish Development
The relationship between phytoplankton and fish development operates through several interconnected pathways:
Direct Consumption: Some minnow species have evolved specialized feeding mechanisms that allow them to filter phytoplankton directly from the water. Through pump filtering and specialized gill rakers, these fish create negative pressure in their mouths, drawing water across comb-like structures that trap microscopic algae cells.
Indirect Support Through Zooplankton: Many fish fry cannot consume phytoplankton directly but depend entirely on zooplankton that graze on algae. Rotifers feed on bacteria and phytoplankton, reproducing rapidly when food is abundant. This creates dense populations of appropriately sized prey for fish larvae during their critical first weeks of life.
Nutrient Cycling: As fish consume zooplankton and excrete waste, they help recycle nutrients throughout the water column, supporting continued phytoplankton growth and maintaining a healthy, balanced ecosystem.
Beyond Minnows: Other Native Species That Benefit
The importance of phytoplankton extends far beyond minnows:
Bluegill (Lepomis macrochirus): Newly hatched bluegill begin consuming microinvertebrates and phytoplankton until they reach a size where they can graze on periphyton—a combination of algae, fungi, bacteria, and the macroinvertebrates that feed on this material.
Largemouth Bass, Walleye, and Other Game Fish: Even predatory game fish species depend on phytoplankton during their earliest life stages. Young bass and walleye fry feed on zooplankton before transitioning to larger prey, making robust plankton populations essential for strong year-class recruitment.
Sunfish Species: Various native sunfish species follow similar developmental patterns, with larvae depending on the zooplankton supported by healthy phytoplankton blooms.
Zooplankton, especially copepods are excellent additions to pond ecosystems. They eat phytoplankton which increases the clarity of your water while allowing phytoplankton to consume excess nutrients and improve your water quality.
Zooplankton also make excellent food for fish fry, minnow and other small organisms promoting a healthy food chain and attacking a diverse array of wildlife to your pond from aquatic organisms to birds and insects. They are the second tier of a ponds ecosystem and are fascinating microorganisms that perform a variety of beneficial functions.
Selenastrum:
Protein and Amino Acids:
Selenastrum contains substantial protein content, typically ranging from 40-50% of dry weight, providing essential amino acids that zooplankton require for growth and reproduction. This protein-rich composition makes it comparable to other premium phytoplankton species used in aquaculture.
Lipids and Fatty Acids: While not as lipid-rich as some marine phytoplankton, Selenastrum produces polyunsaturated fatty acids (PUFAs) including omega-3 and omega-6 fatty acids. These compounds are crucial for zooplankton development, particularly for species like Daphnia, which cannot synthesize these fatty acids independently.
Vitamins and Minerals: This green alga synthesizes B-vitamins, vitamin E, and accumulates essential minerals including iron, zinc, and selenium. The presence of these micronutrients enhances its palatability and digestibility for filter-feeding zooplankton.
Cell Size and Digestibility: With cell dimensions typically between 8-14 micrometers, Selenastrum falls within the optimal size range for consumption by most freshwater zooplankton species. Its thin cell wall and lack of toxic secondary metabolites make it highly digestible.
Scenedesmus
Protein Content
Scenedesmus contains remarkably high protein levels, typically ranging from 50-60% of its dry weight, making it one of the most protein-rich natural food sources available to herbivorous zooplankton. This protein is rich in essential amino acids that support zooplankton growth, reproduction, and survival.
Lipids and Fatty Acids
The algae produces polyunsaturated fatty acids (PUFAs), including omega-3 and omega-6 fatty acids, which are critical for zooplankton development and overall health. These fatty acids cannot be synthesized by most zooplankton and must be obtained from their diet, making Scenedesmus particularly valuable.
Vitamins and Minerals
Scenedesmus is a rich source of B-vitamins, vitamin E, and carotenoids (including beta-carotene and astaxanthin), which support immune function and reproductive success in zooplankton. The algae also provides essential minerals such as iron, magnesium, calcium, and phosphorus.
Digestibility
The relatively thin cell walls of Scenedesmus compared to some other algae make it more easily digestible for many zooplankton species, improving nutrient assimilation efficiency and supporting higher growth rates in consumer populations.
Chlorella Vulgaris
Protein Content
This microalgae contains between 50-60% protein by dry weight, making it one of the most protein-rich organisms on Earth. Beyond protein, chlorella provides essential fatty acids, particularly omega-3 and omega-6 polyunsaturated fatty acids that zooplankton cannot synthesize themselves but require for growth, reproduction, and proper membrane function.
Chlorella also delivers a comprehensive vitamin package including B-complex vitamins, vitamin C, and vitamin E, along with essential minerals such as iron, calcium, magnesium, and zinc. These micronutrients support critical physiological processes in zooplankton, from enzyme function to exoskeleton development. The carotenoid pigments found in chlorella, including lutein and beta-carotene, provide antioxidant protection and contribute to the health and coloration of organisms throughout the food web.
The digestibility of chlorella makes these nutrients readily available to zooplankton. Studies have shown that various zooplankton species, including rotifers, cladocerans like Daphnia, and copepods, thrive when fed diets containing C. vulgaris. The small cell size (typically 2-10 micrometers in diameter) makes it an ideal food source for filter-feeding zooplankton, which can efficiently capture and consume these nutritious cells.
Ankistrodesmus
Protein and Amino Acids
Ankistrodesmus typically contains high protein levels, often comprising 40-50% of its dry weight. This protein is rich in essential amino acids that zooplankton cannot synthesize themselves, making the algae an excellent nutritional match for herbivorous and omnivorous zooplankton species.
Lipids and Fatty Acids
The lipid content of Ankistrodesmus generally ranges from 10-20% of dry weight, though this can vary with environmental conditions and nutrient availability. Importantly, this genus produces polyunsaturated fatty acids (PUFAs), including omega-3 fatty acids that are essential for zooplankton growth, reproduction, and overall fitness. These fatty acids are transferred up the food chain, ultimately supporting fish populations and higher trophic levels.
Vitamins and Minerals
Ankistrodesmus accumulates various vitamins, particularly B-complex vitamins and vitamin E, along with essential minerals such as calcium, magnesium, iron, and zinc. These micronutrients are vital for zooplankton metabolic processes, shell formation (in species like daphnids and copepods), and reproductive success.
Digestibility
The cell wall composition of Ankistrodesmus makes it relatively digestible compared to some other algae species. While not as easily consumed as soft algae like Cryptomonas, most zooplankton species can effectively graze on Ankistrodesmus and assimilate its nutrients efficiently.
Nannochloropsis limnetica
Protein Content
This species boasts a protein content ranging from 40-50% of its dry weight, providing essential amino acids that support zooplankton growth and reproduction.
Lipid Profile
Perhaps most importantly, N. limnetica contains significant levels of polyunsaturated fatty acids (PUFAs), including omega-3 fatty acids like eicosapentaenoic acid (EPA). These long-chain fatty acids are critical for zooplankton development, reproduction, and overall health. Many zooplankton species cannot synthesize these compounds themselves and must obtain them from their diet.
Vitamins and Minerals
The algae also provides essential vitamins and trace minerals that support metabolic functions in zooplankton consumers.
Digestibility: With its small cell size (typically 2-4 micrometers in diameter), circular in shape and with a relatively thin cell wall, N. limnetica is easily consumed and digested by a wide range of zooplankton species, from rotifers to copepods.
Chlamydomonas
Chlamydomonas species serve as a critical food source for zooplankton, providing essential nutrients that fuel freshwater food chains. These unicellular algae are packed with proteins, lipids, and carbohydrates that make them highly digestible and nutritionally valuable for filter-feeding organisms.
The nutritional profile of Chlamydomonas includes high-quality proteins containing essential amino acids, omega-3 fatty acids that support zooplankton growth and reproduction, vitamins including B-complex vitamins and vitamin E, and carotenoid pigments with antioxidant properties. This rich nutrient composition makes Chlamydomonas an ideal primary producer, efficiently converting light energy and dissolved nutrients into biomass that sustains higher trophic levels. They are also a mobile phytoplankton with multiple flagella (whip like tails) that help propel them through water.