Interview Questions for Algae Identification and Classification

Algal cell walls, unlike those of plants, exhibit remarkable diversity in their composition and structure. This variation is a crucial characteristic used in algal identification. The most common types include:

• Cellulose: Many green algae possess cell walls primarily composed of cellulose, a complex carbohydrate. This is similar to plant cell walls, although the specific arrangement can differ.
• Silicate (Silica): Diatoms are easily distinguished by their intricately patterned cell walls made of silica, a form of glass. These ‘frustules’ are remarkably beautiful and their unique patterns are essential for species identification. Think of them as microscopic, exquisitely detailed glass boxes.
• Calcium Carbonate: Some algae, like certain species of green algae (e.g., some Chara species) and certain red algae, incorporate calcium carbonate into their cell walls, providing additional structural support and rigidity. This makes them feel hard and sometimes even crunchy.
• Other Polysaccharides: Many algal groups have cell walls consisting of various complex polysaccharides, sometimes in combination with proteins or other substances. The precise composition and arrangement of these molecules can be specific to a particular algal group or species.

Understanding the cell wall composition provides the first step in identifying an alga. A simple iodine test, for example, can differentiate cellulose-based walls from others.

Microscopy is fundamental to algal identification. The process typically involves these steps:

1. Sample Preparation: A small sample of the algal material is mounted onto a microscope slide, often with a mounting medium to prevent movement and maintain clarity.
2. Light Microscopy: Initial observation is usually performed using a light microscope. This allows for the visualization of cell shape, size, and the presence of characteristic structures like chloroplasts, pyrenoids (sites of starch synthesis), and flagella. Different magnifications are used, starting with a low power to identify potential algal groups and gradually increasing the magnification for detailed species identification.
3. Specialized Microscopy: For finer details, more specialized techniques might be needed. For example, electron microscopy (SEM and TEM) provides high-resolution images revealing the intricate details of cell wall structures and other subcellular components which is essential for differentiating closely related species. Fluorescence microscopy can highlight specific cellular components, such as chloroplasts or specific pigments.
4. Key Feature Identification: Throughout the observation, one should note key features – cell shape, size, arrangement of chloroplasts, type of flagella (if present), cell wall composition, and presence of any other unique structures.
5. Comparison with Known Species: Finally, the observed features are compared with known species descriptions found in taxonomic keys, illustrations, and databases. This stage often requires expertise in algal taxonomy and access to a comprehensive library of algal illustrations and descriptions.

Think of it like a detective investigation, where each clue (cell shape, pigments, etc.) helps you narrow down the possibilities until you reach a positive identification.

These three groups represent vastly different lineages within the algae:

• Diatoms (Bacillariophyceae): These are unicellular algae characterized by their stunningly intricate silica cell walls, called frustules. They are ubiquitous in aquatic environments and are a major component of phytoplankton. Think of tiny, ornamented glass boxes. Their cell walls are a key identifying feature.
• Dinoflagellates (Dinophyceae): Dinoflagellates are mostly unicellular, and often possess two flagella, one transverse and one longitudinal, resulting in characteristic spinning or whirling movement in the water. Many are photosynthetic, but some are heterotrophic or mixotrophic. Many are known to produce toxins, causing harmful algal blooms.
• Green Algae (Chlorophyta): This diverse group includes both unicellular and multicellular species, sharing many characteristics with land plants. They typically contain chlorophylls a and b, and store food as starch, just like land plants. Their cell walls are usually composed of cellulose.

The differences are striking: Diatoms have glass-like cell walls and are always unicellular, dinoflagellates often have two flagella and can be toxic, and green algae share characteristics with plants, and come in various forms from single cells to large seaweeds.

Algal classification relies on a combination of features:

• Cell Structure and Morphology: Cell shape, size, number and arrangement of flagella, presence of cell walls and their composition, and the internal organization of the cell (e.g., the number, shape and arrangement of chloroplasts, the presence of pyrenoids).
• Pigments: The types and relative amounts of photosynthetic pigments (chlorophylls, carotenoids, phycobilins) are crucial for determining taxonomic placement. The color of the alga is often a first clue.
• Storage Products: The type of carbohydrate or lipid used to store energy (starch, paramylon, oils) varies across algal groups.
• Molecular Phylogenetics: Modern techniques using DNA and RNA sequences provide powerful tools for resolving taxonomic relationships and refining classifications based on evolutionary history. This is particularly useful for distinguishing closely related species that may look similar under a microscope.
• Reproductive Strategies: The methods of reproduction (asexual versus sexual) and the types of reproductive structures produced can be useful taxonomic markers.

Imagine classifying them as if you were organizing a vast library, using multiple indices (pigments, storage products, etc.) to find the right shelf (classification).

Cyanobacteria, although often referred to as ‘blue-green algae,’ are actually bacteria, not algae. Their identification relies on characteristics distinct from eukaryotic algae:

• Morphology: Cell shape (coccus, bacillus, filamentous) and arrangement (single cells, chains, colonies) are important features. Look for the presence of akinetes (resting spores) or heterocysts (nitrogen-fixing cells).
• Pigments: Cyanobacteria typically contain chlorophyll a, phycocyanin (blue pigment), and phycoerythrin (red pigment) – hence their often blue-green appearance. The presence and relative amounts of these pigments vary between species.
• Physiology: Some cyanobacteria can fix atmospheric nitrogen, a unique ability that’s often associated with the presence of heterocysts. Other physiological features, like their ability to grow in extreme conditions (high salinity, high temperature) may also be considered.
• Molecular Analysis: As with algae, molecular techniques like 16S rRNA sequencing are increasingly used to identify and classify cyanobacteria to species level, particularly in cases where morphological features are unclear.

Identifying cyanobacteria requires a careful examination of their microscopic characteristics combined with knowledge of their unique physiological capabilities. Unlike most algae, some cyanobacteria have specialized cells for nitrogen fixation.

Algal blooms, or harmful algal blooms (HABs), have significant ecological and economic consequences:

• Oxygen Depletion: Massive algal growth consumes large amounts of oxygen, creating hypoxic (low-oxygen) or anoxic (no-oxygen) zones that can lead to fish kills and the death of other aquatic organisms.
• Toxicity: Many algae produce toxins that are harmful to humans, marine mammals, fish, and birds. These toxins can accumulate in the food chain, posing risks to human health through shellfish consumption.
• Habitat Degradation: Algal blooms can block sunlight, reducing the growth of submerged aquatic plants and impacting the entire food web. They can also alter water clarity and change the chemical composition of the water.
• Economic Impacts: HABs can negatively impact fisheries, tourism, and recreational activities, leading to significant economic losses.

Think of an algal bloom as an uncontrolled population explosion, disrupting the balance of the ecosystem and potentially causing harm.

Algal culturing requires careful attention to detail. The methods vary depending on the species and the intended purpose:

• Culture Media: Specialized culture media are designed to provide the necessary nutrients for algal growth. The composition of the media varies widely, depending on the specific needs of the algal species. Common components include salts, trace elements, and vitamins.
• Sterility: Maintaining a sterile culture is crucial to prevent contamination by other microorganisms. This involves using sterile techniques during media preparation and handling.
• Light and Temperature: Algae require specific light intensities and temperature ranges for optimal growth. These parameters must be carefully controlled and monitored. Light quality (spectral composition) can also significantly influence growth.
• Aeration: Adequate aeration is essential to provide oxygen and to prevent the accumulation of metabolic waste products.
• Culture Vessels: Various culture vessels can be used, from small test tubes to large photobioreactors, depending on the scale and type of culture.
• Subculturing: Regular subculturing is necessary to maintain healthy algal cultures and prevent nutrient depletion or the accumulation of inhibitory substances.

Algal culturing is similar to gardening, but instead of plants, you are cultivating microscopic organisms, and the success depends on providing them with the right environment.

Algae play a crucial role in the global carbon cycle, acting as primary producers in aquatic and terrestrial ecosystems. They utilize photosynthesis to convert atmospheric carbon dioxide (CO₂) into organic carbon, effectively sequestering CO₂ from the atmosphere. This process is fundamental to maintaining atmospheric CO₂ levels and influencing climate regulation.

Imagine the ocean as a giant carbon sink. Phytoplankton, microscopic algae, are the main drivers of this sink, absorbing vast amounts of CO₂. When these algae die, a portion of their carbon sinks to the ocean floor, effectively removing it from the atmosphere for long periods. However, it’s crucial to understand that this process is complex and influenced by factors like ocean currents, water temperature, and nutrient availability. For example, increased nutrient runoff from agriculture can lead to algal blooms, which while initially absorbing CO₂, can later release it back into the atmosphere as the algae decompose. The balance between CO₂ uptake and release is vital for understanding the overall impact of algae on the carbon cycle.

Molecular techniques have revolutionized algal identification, offering greater precision and speed compared to traditional morphological methods. The most common technique is DNA barcoding, which involves sequencing specific regions of the algal genome, such as the 18S ribosomal RNA (rRNA) gene. These sequences act like unique ‘barcodes’ that can be compared to databases of known algal species to identify an unknown sample.

For example, we might extract DNA from a water sample, amplify the 18S rRNA gene using Polymerase Chain Reaction (PCR), and then sequence the amplified product. The resulting sequence is then compared to databases like NCBI GenBank using bioinformatics tools. The closest match indicates the likely species. Other molecular techniques include phylogenetic analysis, using multiple gene sequences to reconstruct evolutionary relationships, and metabarcoding, which simultaneously identifies multiple algal species within a complex sample.

This molecular approach addresses limitations of traditional methods, particularly in identifying cryptic species (species that look similar morphologically but are genetically distinct), and helps in identifying species that are too small or too degraded to be easily identified morphologically.

Algae hold immense promise as a sustainable source of biofuels. Their high growth rates and ability to convert sunlight into energy make them an attractive alternative to fossil fuels. Several approaches are being explored:

• Lipid Production: Many algae species accumulate significant amounts of lipids (oils) within their cells. These lipids can be extracted and processed into biodiesel, a renewable fuel that can be used in existing diesel engines.
• Carbohydrate Production: Some algae produce large quantities of carbohydrates, which can be fermented to produce bioethanol, another type of biofuel.
• Hydrogen Production: Certain algal species can produce hydrogen gas through photosynthesis under specific conditions, offering a clean and sustainable energy source.

However, challenges remain, including optimizing algal cultivation for high lipid or carbohydrate production, developing cost-effective extraction and processing methods, and addressing land and water usage concerns. Despite these challenges, algal biofuel research continues to advance, with the potential to provide a significant contribution to a more sustainable energy future.

Identifying algae in complex environmental samples, such as soil or water with diverse microbial communities, presents significant challenges. The main issues include:

• High species diversity: Samples often contain numerous algal species, many of which may be present in low abundance, making identification difficult.
• Morphological overlap: Many algal species exhibit similar morphologies, especially in their vegetative stages, making visual identification unreliable.
• Degradation: Algae cells can degrade quickly in environmental samples, making morphological examination challenging.
• Contamination: Samples can be contaminated with other microorganisms or debris, hindering algal identification.

To overcome these challenges, researchers often employ a combination of techniques, including microscopy (light, fluorescence, electron), molecular methods (DNA barcoding, metabarcoding), and image analysis. Careful sample preparation and preservation are crucial to minimize degradation and contamination. Advanced statistical and bioinformatics tools are also necessary to analyze the large datasets generated from these analyses.

Nutrient pollution, particularly an excess of nitrogen and phosphorus, has a dramatic impact on algal growth. This phenomenon, often called eutrophication, leads to explosive growth of algae, resulting in harmful algal blooms (HABs). These blooms can deplete oxygen in the water, leading to fish kills and impacting the entire aquatic ecosystem.

Think of it like fertilizing a lawn excessively. The lawn (algae) will grow much faster than intended, potentially choking out other plants and creating an undesirable situation. Similarly, nutrient runoff from agricultural fields, sewage treatment plants, and industrial discharges provides an abundance of nutrients that fuel algal blooms. These blooms can be unsightly, produce unpleasant odors, and even produce toxins that pose risks to human and animal health.

Managing nutrient pollution is essential to mitigate the negative impacts of eutrophication and control harmful algal blooms. Strategies include improving wastewater treatment, implementing sustainable agricultural practices, and controlling stormwater runoff.

Assessing algal diversity involves a multi-step approach that combines field sampling with laboratory analysis. Firstly, a representative water sample is collected, ideally from multiple locations within the study area.

In the lab, the sample is analyzed using various techniques:

• Microscopy: Light microscopy is used to observe and identify algal species based on their morphology (size, shape, chloroplast structure, etc.). More advanced techniques like fluorescence microscopy are employed to detect specific pigments or cellular components.
• Culture methods: Algal cells can be isolated and grown in culture to obtain larger quantities of material for further analysis, allowing for detailed morphological examination and molecular characterization.
• Molecular methods: DNA barcoding and metabarcoding are used to identify algal species based on their genetic sequences. This approach can reveal the presence of species that may be difficult to identify using microscopy alone.

The data obtained from these analyses can be used to calculate various diversity indices, such as species richness (the total number of species), Shannon diversity index (considers both species richness and evenness), and Pielou’s evenness index. This comprehensive approach provides a detailed assessment of algal diversity in a given water sample, aiding in monitoring water quality and understanding ecosystem health.

Several types of algae produce toxins that can be harmful to humans and animals. These toxins, known as cyanotoxins (produced by cyanobacteria, a type of algae), vary in their chemical structure and their effects.

• Microcystins: These are hepatotoxins (liver toxins), causing damage to the liver and potentially leading to liver failure. They can enter the food chain through shellfish or drinking water.
• Anatoxins: These neurotoxins affect the nervous system, causing muscle paralysis and respiratory failure. They are often found in water bodies experiencing algal blooms.
• Saxitoxins: These are potent neurotoxins that can cause paralytic shellfish poisoning (PSP). They accumulate in shellfish that feed on toxic algae, posing a risk to humans who consume contaminated shellfish.
• Cylindrospermopsins: These toxins affect the liver and kidneys, and can also have adverse effects on the immune system.

The effects of algal toxins can range from mild gastrointestinal symptoms to severe organ damage and even death. The severity depends on factors such as the type and concentration of toxin, the route of exposure, and the individual’s susceptibility. Regular monitoring of water bodies for the presence of harmful algae and their toxins is crucial to protect public health and the environment.

Morphological identification of algae, relying solely on observable physical characteristics like size, shape, and cellular arrangement, has significant limitations. The biggest issue is that many algal species exhibit high phenotypic plasticity – meaning their appearance can change dramatically depending on environmental conditions such as nutrient availability, light intensity, and temperature. This makes definitive identification based on morphology alone unreliable. For example, a diatom species might appear quite different under nutrient-rich versus nutrient-poor conditions, potentially leading to misidentification.

Furthermore, many species show considerable overlap in morphological characteristics, making differentiation challenging even under ideal conditions. Microscopic techniques often require specialized expertise and high-resolution microscopy to identify subtle distinguishing features. Finally, some algal groups are morphologically very similar, making even experienced microscopists prone to errors without the aid of molecular techniques.

Proper sample preservation is crucial for accurate algal analysis as it prevents degradation and changes in algal morphology and composition. The choice of preservation method depends on the subsequent analytical techniques. For instance, if you plan to conduct microscopic identification, preserving samples with Lugol’s iodine solution is commonly used. This solution effectively fixes the cells, preventing them from shrinking or bursting, ensuring the preservation of their structures. It’s important to note that Lugol’s iodine is not suitable for all analyses, particularly pigment analysis, as it can interfere with pigment extraction. For pigment analysis, freezing samples rapidly in liquid nitrogen is a better method. Other methods include using formalin, which, however, needs careful handling and should only be employed by trained individuals.

Ideally, samples should be preserved as soon as possible after collection to minimize changes and degradation of the organisms. For example, if you are analyzing a bloom of harmful algae in a lake, rapidly preserving samples is essential to capture the species present in their natural state. Improper preservation can lead to significant errors in species identification and quantification, potentially impacting environmental monitoring or ecological studies.

Algal bioassays measure the growth response of algae to various stimuli, such as pollutants or nutrient additions. Data interpretation involves assessing the growth rate or biomass production of the algae under different conditions. A common approach is to compare the growth in a control group (untreated) against experimental groups (exposed to different concentrations of the stimulus). Growth is often quantified by measuring cell numbers, chlorophyll concentration, or dry weight.

For example, if you are assessing the toxicity of a new chemical, you would compare algal growth in the control group (no chemical) with groups exposed to varying concentrations of the chemical. If the growth rate decreases significantly in higher concentration groups compared to the control, this would suggest toxicity. A dose-response curve is often generated to illustrate this relationship. EC₅₀ (effective concentration that causes 50% growth inhibition) is a critical metric derived from this curve; it shows the concentration of the pollutant that causes a 50% reduction in algal growth relative to the control. Statistical tests like ANOVA or t-tests are often employed to determine statistically significant differences between treatment groups.

Algal growth in aquatic environments is a complex interplay of several factors.

• Nutrient availability: Nitrogen and phosphorus are key nutrients driving algal growth; an excess leads to eutrophication and algal blooms.
• Light intensity and quality: Algae require light for photosynthesis. Light intensity and wavelength availability strongly influence their growth and species composition.
• Temperature: Optimal temperature ranges vary by algal species. Temperature changes can affect metabolic rates and ultimately algal growth.
• Water chemistry: pH, salinity, and the presence of certain ions or pollutants can significantly affect algal growth and species diversity.
• Grazing pressure: Zooplankton and other herbivores can significantly regulate algal populations.
• Water flow and mixing: Water movement affects nutrient supply, light penetration, and dispersal of algal cells.

Consider a lake experiencing eutrophication. High nutrient loads (phosphorus from agricultural runoff, for example) lead to excessive algal growth, potentially forming harmful algal blooms, impacting water quality, and harming aquatic life. Understanding the interplay of these factors is crucial for managing and predicting algal growth in aquatic systems.

Quantifying algal biomass involves measuring the total amount of algal material present in a sample. Several methods are available:

• Cell counting: Microscopic examination allows for direct counting of individual algal cells or colonies using a haemocytometer or automated cell counters. This is suitable for larger algae that are easily distinguishable.
• Chlorophyll concentration: Chlorophyll is a key photosynthetic pigment in algae. Its concentration in a water sample provides a good indicator of algal biomass, measured spectrophotometrically after extraction from algal cells.
• Dry weight: Algal samples are filtered, dried in an oven at a specific temperature, and weighed. This method provides a direct measure of algal biomass but can be time-consuming and less sensitive than other methods.
• Optical density: Turbidity or optical density of water samples measured using a spectrophotometer can indirectly assess algal biomass, though this is less precise than direct measurements as it is affected by other suspended particles in the water.

The best method depends on factors like the type of algae, the research question, and available resources. For example, in a study of phytoplankton community composition in a river, using a combination of cell counts and chlorophyll measurements might provide a more comprehensive assessment of the overall algal biomass and species diversity.

Pigment analysis is a powerful tool in algal identification because different algal groups possess characteristic pigment profiles. Algae utilize various pigments for photosynthesis, including chlorophylls (a, b, c), carotenoids (e.g., β-carotene, fucoxanthin), and phycobilins (phycocyanin, phycoerythrin). By extracting and quantifying these pigments using High-Performance Liquid Chromatography (HPLC) or spectrophotometry, we can obtain a ‘pigment fingerprint’ that can be used to identify algal taxa or even to estimate the relative abundance of different algal groups in a mixed sample.

For example, the presence of fucoxanthin indicates the presence of diatoms or brown algae (Phaeophyceae), while phycocyanin is a hallmark of cyanobacteria. The ratio of different chlorophyll types can also provide valuable taxonomic information. Combining pigment analysis with morphological observations and other molecular data can lead to more accurate and reliable identification, particularly in samples containing various algal species.

Algae have numerous applications in wastewater treatment, primarily due to their ability to efficiently remove nutrients and pollutants. They are used in several ways:

• Wastewater nutrient removal: Algae effectively assimilate nitrogen and phosphorus, key nutrients that cause eutrophication. Algal cultivation systems can reduce these nutrients to levels that are safe for discharge.
• Bioremediation: Algae can remove various pollutants, such as heavy metals and organic contaminants from wastewater, by absorbing or biotransforming these pollutants.
• Biofuel production: Algal biomass produced during wastewater treatment can be harvested and used to produce biofuels, adding economic value and reducing reliance on fossil fuels.
• Wastewater treatment in constructed wetlands: Algae are integral components of constructed wetlands, artificial ecosystems designed for wastewater treatment. Algae contribute to nutrient removal and oxygenation.

Using algae in wastewater treatment offers a sustainable approach by converting a waste stream (wastewater) into a resource (algal biomass) with potential for energy production or other applications. The process can improve water quality and contribute to a circular economy.

The primary difference between benthic and planktonic algae lies in their habitat. Benthic algae are attached to a substrate, such as rocks, sediments, or other aquatic plants, living on the bottom of a water body. Think of them as the ‘plants’ of the underwater world. Planktonic algae, on the other hand, are free-floating, drifting with the currents in the water column. They form the base of the open-water food web, similar to phytoplankton in the ocean.

Imagine a lake: the algae growing on the rocks at the bottom are benthic, while the green ‘soup’ suspended in the water is planktonic. This distinction is crucial for understanding nutrient cycling, community dynamics, and even water quality monitoring, as different species thrive in each environment.

Ethical considerations in algal research are multifaceted. Environmental impact is paramount; researchers must minimize disturbance to natural habitats during sampling and cultivation. We must consider the potential for the introduction of invasive species or the unintentional release of genetically modified algae. Sustainability in cultivation practices is also key; methods should be efficient but not resource-intensive.

Furthermore, intellectual property rights and the potential commercialization of algal discoveries must be handled responsibly, ensuring fair access to benefits and avoiding biopiracy. Finally, transparency and the open sharing of research data are vital to ensure the integrity and advancement of the field. For example, if studying a rare algal species, we should prioritize conservation efforts and avoid harming the population.

Algal life cycles exhibit significant diversity. Many algae reproduce both sexually and asexually, often alternating between generations. A common cycle is haplodiplontic, involving alternating haploid (gametophyte) and diploid (sporophyte) phases. The gametophyte produces gametes (sex cells) that fuse to form a zygote, developing into the diploid sporophyte. The sporophyte then produces haploid spores through meiosis, which germinate to form new gametophytes.

• Haplontic: The dominant phase is haploid, with the diploid zygote undergoing meiosis immediately.
• Diplontic: The dominant phase is diploid, with meiosis producing haploid gametes.
• Isomorphic alternation of generations: The haploid and diploid generations are morphologically similar.
• Heteromorphic alternation of generations: The haploid and diploid generations differ significantly in morphology.

Understanding these life cycles is critical for cultivating and managing algae, as it influences aspects like spore production and genetic diversity.

Flow cytometry is a powerful tool for analyzing algal populations. It allows for high-throughput, rapid analysis of individual cells based on their light scattering and fluorescence properties. Cells are passed through a laser beam, and the scattered and emitted light is measured. This data can be used to differentiate species based on size, shape, pigment content, and other cellular characteristics.

For example, by using specific fluorescent dyes that bind to chlorophyll or other cellular components, we can quantify the abundance of different algal groups within a sample. This is particularly useful for monitoring harmful algal blooms or assessing the diversity of algal communities in aquatic ecosystems. Think of it as a ‘cell sorter’ that can identify and count different types of algae very quickly.

Isolating and purifying algal cultures requires meticulous techniques to avoid contamination. Streak plating on agar media is a common method, diluting the sample to obtain individual colonies. Micromanipulation, using a microscope and fine needles, allows for the isolation of single cells or filaments. Another effective technique involves using serial dilutions in liquid media, eventually leading to cultures containing single cells that can then be grown individually.

Flow cytometry can also be employed for isolating specific algal cells based on their properties. Once isolated, cultures must be maintained under sterile conditions to prevent contamination from bacteria, fungi, or other algae. Regular microscopic examination is crucial to ensure the purity of the culture.

Contamination in algal cultures is a major challenge. It can be identified through microscopic examination, looking for the presence of unwanted organisms. Changes in culture appearance, such as unusual color, odor, or turbidity, can also indicate contamination. Molecular methods, such as PCR, can be used to detect specific contaminants.

Prevention relies on strict sterile techniques: using sterile media and equipment, working in a laminar flow hood, and regularly sterilizing culture vessels. Careful selection of the initial sample and appropriate growth conditions can also minimize contamination risk. If contamination occurs, discarding the contaminated culture and starting afresh is often necessary.

Algae play a crucial role in aquatic food webs as primary producers. They convert light energy into chemical energy through photosynthesis, forming the base of the food chain. Herbivorous zooplankton graze on algae, which are then consumed by larger organisms like fish and other invertebrates. This transfer of energy supports the entire aquatic ecosystem.

In some ecosystems, specific algae species may be keystone species, dominating the primary production and influencing the abundance and distribution of other organisms. Understanding the role of algae in food webs is essential for managing aquatic resources and assessing the impacts of environmental change, such as nutrient pollution or climate change. Their role is fundamental; without them, the whole ecosystem collapses.