Rock Creek is a stressed environment. Its waters are choked with algal blooms periodically during the year. On August 4th, we measured visibility into the water column in three different places at about 18” (4 decimeters). We have seen worse, but this is not good. Algae thrive on nitrogen and phosphorus. Clearly, we have too much nitrogen and phosphorus in our waters.
We are doing something about it!
RRC volunteers just planted two floating structures about a month ago. One is an island, the other a wetland. We are studying how these different, but similar, technologies work. We want to know if a floating wetland or a floating island work best in our estuary.
These structures mimic wetlands and are useful for
• De-nitrification for Nitrate removal
• Total Suspended Solids (TSS) reduction
• Phosphorus reduction and sequestration
• Fish & Wildlife habitat, food, shade and protection
• Shoreline protection & Erosion Control
And they look better than wooden bulkhead! Here is a picture of a floating island planted with mature hibiscus that happens to be in bloom right now!
RRC’s islands are resting comfortably next to a dock in White’s Cove awaiting installation. One will be placed at Pasadena Yacht Yard — Thank You PYY!! The second will be permanently installed somewhere on the creek in the coming weeks. We are looking for a public or semi public place with bulkheads.
This is how they looked yesterday (8/8/16)
We planted five different plants in quadrants to assess how each performs. The fence keeps predators off the islands until they are well enough established to endure some predation (generally geese will leave matter plants alone as they prefer the young grass). We spent some time designing the fence to remain effective for a full year while the plants grow. We now know how to build this fence so it remains sturdy.
We plan to use the insights gained with these experiments to guide us as we plant and install more floating islands around our creek.
Here is a breakdown of the species planted:
1) Salt meadow cordgrass (left image lower left) is doing very well indeed. It has grown from 10-14” to over 24” while adding significant number of new stems! It is performing well in both the submerged and slightly wet locations so far. Young plants of this species are “goose candy” which is why these islands are protected by fencing.
Spartina patens, also known as salt marsh hay, is a native cordgrass native that can be found in marshlands and is a hay-like grass found in the upper areas of brackish coastal salt marshes. It is a slender and wiry plant that grows in thick mats 30-60 cm high, green in spring and summer, and turns light brown in late fall and winter. The stems are wispy and hollow, and the leaves roll inward and appear round. Because its stems are weak, the wind and water action can bend the grass, creating the appearance of a field of tufts and cowlicks and is found in high marsh zones where it is covered at times by high tides. (Paraphrased from Wikipedia)
2) Smooth cordgrass (left image lower right and right image upper left) struggled initially, but is taking off now doing very well. These plants were all under 4” when planted, most were around 2-3”. There are more stems now, they are fuller, greener and now stand 10-12”. These are growing well while inundated (as expected).
Spartina alterniflora, also referred to as saltmarsh cordgrass, or salt-water cord grass, is a perennial deciduous grass which is found in intertidal wetlands, especially estuarine salt marshes. It grows 1-1.5 m tall (3-5 feet,) and has smooth, hollow stems which bear leaves up to 20-60 cm (8 inches-2 feet) long and 1.5 cm (1/2 inch) wide at their base, which are sharply tapered and bend down at their tips and is intolerant of shade. Its roots are an important food resource for geese. It can grow in low marsh (frequently inundated by the tide) as well as high marsh (less frequently inundated), but it is usually restricted to low marsh because it is outcompeted by saltmeadow cordgrass in the high marsh and grows in a wide range of salinities. It may be the “single most important marsh plant species in the estuary” of Chesapeake Bay. (Paraphrased from Wikipedia)
3) Blue flag iris (Upper right quadrant in both pictures) sows signs of some stress (older leaves have brown fringes), but newer growth is healthy and green. When planted, all the iris were 3-6”. The best performing now measure 8 to 10”. Iris planted in the margins where it’s wet all the time are mostly doing well.
Iris versicolor, Blue flag iris, is a hardy lakeshore perennial herb typically found in the shallow waters of pond edges, sedge meadows, marshes, along stream banks and in forested moist soil wetlands. Blue flag iris forms sword-like foliage 2-3′ tall growing from thick creeping rhizomes. The elegant flowers of Blue flag iris are 2-4″ across and usually light to deep blue and bloom from May to July.
4) Hibiscus was not planted on the floating wetland because it does not like to be inundated all the time. Predictably, inundated plants are doing less well (most have perished). the foliage is healthy and the plants are growing well. When planted, these plants were about 10” They measure 15-18” now.
Hibiscus is a genus of flowering plants in the mallow family, Malvaceae. The genus is quite large, containing several hundred species that are native to warm-temperate, subtropical and tropical regions throughout the world. Member species are often noted for their showy flowers and are commonly known simply as hibiscus, or less widely known as rose mallow. The genus includes both annual and perennial herbaceous plants, as well as woody shrubs and small trees. Native hibiscus are tolerant of shade, grow to 4’ and feature beautiful white flowers with a pink center in late summer. (Paraphrased from Wikipedia)
5) Cardinal flower (they are located in the upper left quadrant of the photo on the left and on the lower right of the photo on the right) is struggling most. From time they were planted, all seemed to die back, especially the flooded plants. The plants that are not flooded are all rebounding and looking healthier. Most plants have several leaves and are 3-3” tall. Interestingly, the plants on the fringe are the tallest. We wonder if the young plants were victims of predation?
Lobelia cardinals is a perennial herbaceous plant that grows up to 1.2 m (4 ft) tall and is found in wet places, streambanks, and swamps. The leaves are up to 20 cm (8 in) long and 5 cm (2 in) broad, lanceolate to oval, with a toothed margin. The flowers are usually vibrant red, deeply five-lobed, up to 4 cm across; they are produced in an erect raceme up to 70 cm (28 in) tall during the summer to fall and are primarily pollinated by the ruby-throated hummingbird