Question

Young lakes are often clear and with little plant life. Such lakes are called a. oligotrophic. b. eutrophic. c. lotic. d. lentic. e. pelagic.

Short answer

The correct answer is a. oligotrophic.

Step-by-step solution

Understanding the Terms

Different terms are used to describe lakes. An oligotrophic lake is usually found in a cold region and has a low nutrient level, making it clear with little plant life. On the other hand, a eutrophic lake, usually warmer, is nutrient-rich and thus abundant with plants and algae. Lotic bodies are characterized by flowing water like rivers, while lentic bodies are stationary waters like lakes or ponds. The term 'pelagic' typically refers to the open water areas of a sea or ocean.

Identifying the Correct Answer

Given that the lake described in the question is clear and has little plant life, it aligns with the description of an oligotrophic lake.

Key concepts

Eutrophic Lake

Unlike the young, clear, and sparse oligotrophic lakes, eutrophic lakes are often depicted as ecologically mature water bodies.

These lakes are characterized by high levels of nutrients such as nitrogen and phosphorus, which promote the growth of aquatic plants and algae. The profusion of plant life not only gives these lakes a murky appearance but also can lead to decreased oxygen levels in the water, particularly when excessive algae growth dies and decomposes – a process known as eutrophication. This can have serious consequences for marine life, often resulting in diminished biodiversity as species intolerant to lower oxygen levels perish.

Eutrophication can be a natural aging process for lakes, but it is often accelerated by human activities such as agriculture runoff and urban wastewater discharge. Therefore, understanding the implications and causes of eutrophic conditions is crucial for environmental conservation and management efforts.

Lotic and Lentic Bodies of Water

The difference between lotic and lentic bodies of water is primarily based on the movement of water.

Lotic bodies of water are those with continuously flowing water, such as streams, creeks, and rivers. Lotic systems are dynamic, their water constantly reshaped by the forces of the current, and they are defined by the directionality of their flow. In this environment, organisms are adapted to resist the force of moving water.

In contrast, lentic bodies of water include stationary or relatively still waters found in lakes, ponds, and wetlands. In these ecosystems, water movement is primarily driven by wind, thermal stratification, or man-made disruptions. The calm waters of lentic systems support different kinds of flora and fauna that are adapted to stable conditions.

Understanding the characteristics of these water bodies is important for ecologists studying habitat requirements and for policymakers making informed decisions about water management and conservation.

Pelagic Zone

The pelagic zone is an open ocean area and is one of the largest ecosystems on Earth. Extending from the water's surface deep into the darkened abyssal depths, the pelagic zone is categorized by depth into different layers, each hosting unique communities of organisms.

These layers range from the uppermost epipelagic zone, where sunlight enables photosynthesis, down to the deep mesopelagic and bathypelagic zones, where light wanes and ceases entirely. The inhabitants of these depths comprise species with specialized adaptations to survive in a realm of high pressure, low oxygen, and scarce food availability.

The pelagic zone is critical for marine life, providing breeding, feeding, and migratory routes for many species. Its health reflects on global biodiversity and ecosystem services such as climate regulation. Conservation efforts here often face challenges due to its vast and international nature but are essential in maintaining the planet's overall ecological balance.