Chesapeake Bay Grasses Introduction • • • • • • • Wild Celery Southern Naiad Red-Head Grass Water Stargrass Widgeon Grass Common Waterweed Eelgrass Salinity and the Chesapeake Bay • Submerged aquatic vegetation has specific salinity requirements, although some have a wide salinity tolerance range. Terms and Salinity levels Euryhaline vs. Stenohaline • “eury” means wide • Organisms that are adapted to tolerate a wide variety of salinities. • Euryhaline organisms are commonly found in habitats such as estuaries and tide pools where the salinity changes regularly. • Some organisms are euryhaline because their life cycle involves migration between freshwater and marine environments, as is the case with striped bass and eels. • “steno” mean narrow • Organisms that can only survive within a narrow range of salinities. • Most freshwater organisms are stenohaline, and will die in seawater, and similarly most marine organisms are stenohaline, and cannot live in fresh water. • Includes crayfish, most species of trout, and darters Plant Anatomy Rhizome – mass of roots Turion - specialised overwintering bud produced by aquatic herbs Monocot – single cotyledon seed Dicot – two seed halves Wild Celery (Vallisneria americana Micheux) • This perennial monocot has long slender leaves with a light green stripe down the center of the leaf. • It is found throughout the Bay in fresh water but can tolerate salinities of up to 12-15 ppt. • Wild celery stabilizes shorelines and tolerates wave • action better than most SAV. • It spreads vegetatively through turions, rhizomes,and seeds (male flowers produce pollen that when released at surface, fertilize the female flowers). • The plants are excellent food for waterfowl and provide habitat for fish and invertebrates. Vallisneria has been used to monitor pollution in rivers. Southern Naiad (Najas guadalupensis (Spreng) Magnus) • • • • • • • • Submerged annual monocots form dense mats of vegetation. Small flowers and fruits are almost entirely hidden at the leaf bases. Leaves are dark green to greenish purple, opposite or in whorls of three. Naiads grow primarily in freshwater streams, and freshwater to brackish tidal Bay tributaries. Southern naiad reproduces by seeds and fragmentation. Fragments can be seen floating at the water’s surface. Pollination takes place underwater. Naiad vegetation and seeds are consumed by waterfowl and in some cases are second only to wild rice as a food source. Redhead Grass (Potamogeton perfoliatus L.) • • • • • Redhead grass is a perennial SAV commonly found in fresh to brackish water of up to 20ppt salinity. It produces winter buds that allow it to establish itself vegetatively, while pollination occurs as spikes of tiny flowers emerge from leaf axils on ends of plant stems. Flower spikes extend above the water surface and the pollen is carried by wind. As fruits mature they sink below the surface where they release seeds. This SAV is an excellent food source for waterfowl. Water Stargrass (Heteranthera dubia (Jacq.) MacMillan) • • • • • • A perennial monocot with dark green leaves with small starshaped yellow flowers that float or rise above the water surface. The plants grow in large, tangled rooted masses. Found in quiet bodies of water with salinities of up to 5 ppt. The plants spread both vegetatively through the roots, and through seed. Flowers that do not reach the water’s surface remain closed and self-pollinate. The leaves are eaten by ducks and other waterfowl, and the plants provide habit for fish and invertebrates. Common Waterweed (Elodea canadensis Micheaux) • • • • Perennial monocot with branching stems; narrow leaves in whorls of 3 at stem nodes, with whorls closer together at tips of plant. Elodea is found in fresh to brackish slow-moving or calciumrich waters; their salinity tolerance is not well documented. Male flowers rise on long stalks and split open, spreading pollen onto the water's surface where it drifts to fertilize female flowers. Ducks, beaver and muskrat consume this plant. Widgeon Grass (Ruppia maritime) • • • • • • Linear, thread-like leaves are 3 to 10 cm (1 ¼ in to 4 in) long and 0.5 mm (<1/32 in) wide; these are arranged alternately along slender, branching stems. Leaves have a basal sheath and a rounded tip. Widgeon grass has an extensive root system of branched, creeping rhizomes that lack tubers. Tolerates a wide range of salinity, from the slightly brackish upper and mid-Bay tributaries to near seawater salinity in the lower Bay, has also been reported to grow in the freshwater parts of some estuaries. Can also be found growing in ditches alongside roads and agricultural fields where it derives its other common name, ditch grass In more saline lower Bay areas, widgeon grass and eelgrass are the dominant bay grass species. Widgeon grass is most common in shallow areas with sandy substrates, although it occasionally grows on soft, muddy sediments. High wave action can damage the slender stems and leaves of widgeon grass. It is also one of the more valuable waterfowl food sources and all parts of the plant have nutritional value Eelgrass (Zostera marina) • • • • • • Zostera marina is found on sandy substrates or in estuaries submerged or partially floating. Most Zostera are perennial. They have long, bright green, ribbon-like leaves, about 1 cm wide. Short stems grow up from extensive, white branching rhizomes. The flowers are enclosed in the sheaths of the leaf bases, the fruits are bladdery and can float. Zostera beds are important for sediment deposition, substrate stabilization, as substrate for epiphytic algae and microinvertebrates, and as nursery grounds for many species of economically important fish and shellfish. Zostera often forms beds in bay mud in the estuarine setting. It is an important food for Brant Geese and Wigeons, and even (occasionally) caterpillars of the grass moth Dolicharthria punctalis.