Understanding the diverse environments of coral reefs and biomes highlights the relationship between species and their surrounding abiotic factors.
Conditions for Coral Reef Formation
Coral reefs, known as the "rainforests of the sea", are biodiversity hotspots. Their formation is a delicate balance of specific abiotic factors.
Image courtesy of Toby Hudson
Water Depth
- Shallow Environments: The majority of coral species flourish in waters less than 25 metres deep due to the symbiotic relationship with zooxanthellae, tiny algae that need sunlight for photosynthesis.
- Sunlight Absorption: Clear waters ensure sunlight penetrates deeply, which is crucial for the photosynthesis of symbiotic algae living within coral tissues.
pH
- Alkaline conditions: A pH range of 7.8 to 8.4 is ideal. It supports the precipitation of calcium carbonate, essential for forming coral skeletons.
- Buffering capacity: The surrounding seawater acts as a buffer, resisting large pH changes which might harm the reef.
Salinity
- Consistent salinity: Corals are adapted to salinity levels between 34-37 ppt. Sudden changes in salinity, due to freshwater influx from heavy rainfall or glacial melt, can stress coral communities.
Clarity
- Clear waters: Coral reefs require sediment-free waters. Excessive sediments, often from coastal development or agriculture runoff, can smother corals, hampering their growth and reproduction.
Temperature
- Tropical climates: Coral reefs primarily exist in the tropics because corals need temperatures between 23°C to 29°C. Temperatures outside this range can lead to coral bleaching, where corals expel their symbiotic algae.
Role of Abiotic Factors in Terrestrial Biome Distribution
Terrestrial biomes span the globe, each characterised by its unique set of abiotic conditions which, in turn, influence its flora and fauna.
Temperature and Rainfall Patterns
- Latitude and altitude: Regions closer to the equator experience warmer temperatures. Conversely, as you move towards the poles or ascend in altitude, cooler temperatures prevail.
- Oceanic influence: Proximity to oceans or large water bodies often leads to milder temperatures and higher humidity due to the moderating effect of water.
Biomes: Characterised by Environmental Factors and Biodiversity
Across the globe, biomes demonstrate how flora and fauna adapt to their environments. Despite being geographically separated, similar biomes can exhibit species with analogous features due to convergent evolution.
Concept of Convergent Evolution
- Similar adaptations in diverse locations: For example, the cacti in American deserts and the euphorbs in African deserts have developed similar adaptations for water storage, even though they're not closely related.
Climate Conditions of Various Biomes
Tropical Forest
- Temperature: Steady throughout the year, averaging between 24°C to 27°C.
- Rainfall: High annual precipitation, frequently 2000-10000 mm. Often, there are distinct wet and dry seasons.
- Biodiversity: Home to over half of the world's species, including numerous endemic species.
Shaheed island, andamans, tropical forest
Image courtesy of Vyacheslav Argenberg
Temperate Forest
- Temperature: Seasons are more pronounced. Winters can reach -30°C, while summer temperatures may rise to 30°C.
- Rainfall: Year-round precipitation, accumulating to 750-1500 mm annually.
- Flora and Fauna: Trees like oaks, beeches, and maples dominate. Mammals, birds, and insects are abundant.
Image courtesy of さかおり
Taiga (Boreal Forest)
- Temperature: Cold is the defining feature. Winters frequently hit -50°C, while summers remain cool, averaging 20°C.
- Rainfall: Primarily snowfall, amounting to 500-1000 mm annually.
- Characteristic species: Coniferous trees like spruce, fir, and pine dominate. Lynx, bears, and moose are typical fauna.
Norwegian boreal forest in early winter.
Image courtesy of Orcaborealis
Grassland
- Temperature: Winters might drop to -20°C, while summers can reach up to 30°C.
- Rainfall: Periodic, often between 250-750 mm yearly.
- Diversity: Grasses are predominant. Large herbivores like bison, antelopes, and zebras, as well as predators like lions and wolves, can be found.
Image courtesy of Shizhao
Tundra
- Temperature: Harshly cold, with winter temperatures going down to -40°C. Summers are brief and cool, peaking at 12°C.
- Rainfall: Primarily snow, totals range from 150-250 mm yearly.
- Life in the Tundra: Dwarf shrubs, mosses, and lichens dominate. Adapted animals like the Arctic fox, snowy owl, and caribou roam here.
Image courtesy of Michael Barera
Hot Desert
- Temperature: Extreme daily fluctuations, from blistering midday highs of 45°C to night-time lows of 20°C.
- Rainfall: Scarce, often less than 250 mm annually.
- Survivors of the desert: Plant life like cacti have adapted to store water. Animals like camels, desert rats, and lizards have evolved to cope with the arid conditions.
Image courtesy of Summer kamal el deen
FAQ
Temperature, largely influenced by latitude and altitude, is a crucial determinant for biome distribution. For instance, as one moves closer to the equator, temperatures rise, leading to the establishment of tropical rainforests. Conversely, moving away from the equator or increasing in altitude brings about colder climates, resulting in biomes like the taiga or tundra. Each biome's specific flora and fauna are adapted to the temperature ranges typical for their environment. For example, the animals in the tundra have adapted to survive extremely cold conditions, while tropical rainforest inhabitants are well-suited to a consistently warm climate.
The buffering capacity of seawater refers to its ability to resist changes in pH. This is crucial for coral reefs because they thrive in a relatively narrow pH range, between 7.8 to 8.4. Within this range, calcium carbonate precipitation is favoured, which is vital for corals to build their calcium carbonate skeletons. If the seawater's pH drops (becomes more acidic), it can lead to reduced calcium carbonate availability, hindering coral growth and making existing structures more fragile. Thus, the natural buffering capacity of seawater helps maintain conditions conducive for coral health, growth, and skeletal formation.
Coral reefs play a vital role in coastal protection by acting as natural barriers that reduce the impact of waves, storms, and surges. Their complex structures dissipate the energy of waves, thereby lessening wave action and preventing erosion of coastlines. This buffering capability is especially crucial for low-lying islands and coastal regions which are susceptible to the effects of rising sea levels and storm surges. Without coral reefs, these areas would face increased erosion, potentially leading to loss of land, damage to infrastructure, and displacement of communities. Thus, maintaining healthy coral reefs is not just essential for marine biodiversity but also for coastal resilience.
Studying biomes with similar environmental conditions but located in different regions offers insights into the concept of convergent evolution and the adaptability of life. Despite geographical separation, similar environmental pressures lead to analogous solutions in different species. By comparing these biomes, researchers can understand how distinct evolutionary pathways can lead to similar biological outcomes. Additionally, these studies offer valuable lessons in biodiversity conservation. Understanding how species in different regions adapt to similar challenges can help formulate conservation strategies, especially in the face of global challenges like climate change.
Coral reefs are termed the "rainforests of the sea" due to their unparalleled biodiversity. Even though they cover less than 0.1% of the ocean's surface, they house approximately 25% of all marine species. Just like rainforests, which teem with a variety of species in a relatively small area, coral reefs are biodiversity hotspots. They offer a complex three-dimensional structure that provides shelter, breeding grounds, and feeding areas for countless marine organisms, from the smallest plankton to large predatory fish. Their significance extends beyond biodiversity; they provide coastal protection, tourism opportunities, and sources for potential medicines.
Practice Questions
Water depth plays a pivotal role in coral reef formation because most coral species predominantly exist in shallow waters, usually less than 25 metres deep. This shallowness allows for adequate sunlight penetration, essential for the photosynthesis of symbiotic algae called zooxanthellae living within coral tissues. Water clarity is equally crucial as clear waters ensure deeper light penetration. Sediment-rich or turbid waters reduce sunlight access, hampering the photosynthetic process of the zooxanthellae. The health of corals largely depends on this symbiotic relationship because zooxanthellae provide vital nutrients to the corals in exchange for protection and compounds they require for photosynthesis.
Convergent evolution in the context of biomes refers to the phenomenon where unrelated species, although geographically distant, evolve similar traits as a response to analogous environmental challenges. These shared adaptations arise independently due to the need to survive under comparable conditions rather than shared ancestry. For instance, within the hot desert biomes of different continents, the American cacti and African euphorbs have both developed fleshy stems for water storage and spines for deterring herbivores. While these plants are not closely related, the harsh desert environment has moulded them to adopt strikingly similar survival strategies.
