While not a prominent aspect of the landscape at Point Reyes, freshwater aquatic plants play an important role in maintaining biodiversity and the health of riparian ecosystems. Freshwater plants, also known as aquatic macrophytes, have adapted to survive in locations where water is the dominant feature of the landscape. Where other plants would not survive due to an excess of water, aquatic plants have special structures that allow them to thrive in a water rich environment. Additionally, aquatic plants have adapted to live in an environment that is subject to substantial changes in conditions. In shallow freshwater environments, water temperatures can vary, affecting the level of photosynthetic activity for organisms that rely on that process for energy. Furthermore, the level of dissolved oxygen in the water can vary, leading to difficulties in respiration.
To live in such a challenging environment, freshwater aquatic macrophytes have developed adaptations that facilitate their existence in a water rich environment. Compared to non-aquatic plants, aquatic macrophytes possess a relatively thin cuticle (a protective, wax-like coating that minimizes plant water loss), which aids in the diffusion of carbon dioxide (CO2) and the dissolved oxygen (O2) that can sometimes be limited in an aquatic environment. To better facilitate energy production, chloroplasts, which are used in plants' photosynthetic process, are centered in the upper leaf area, to maximize potential light exposure. To support the leaves at a level in the water column which would be conducive to photosynthesis, the stems of aquatic macrophytes contain air pockets which aid in maintaining buoyancy. Finally, aquatic macrophytes are typically perennial, and do not reproduce through seeds, instead being typified by vegetative reproduction, where new plants grow from the progenitor's roots or rhizomes.
Despite the challenges inherent in living in an aquatic environment, freshwater ecosystems possess exceptional levels of biodiversity in plant life.
Where to Find Freshwater Aquatic Plants
Aquatic Plants of Point Reyes National Seashore
Evens, Jules G. Natural History of the Point Reyes Peninsula. Berkeley: University of California Press, 2008.
Faber, Phyllis M. Common Wetland Plants of Coastal California. Mill Valley: Pickleweed Press, 1996.
Enger, Eldon D., and Bradley F. Smith. Environmental Science: A Study of Interrelationships. New York: McGraw-Hill, 2000.