Salt Spray - Like a giant margarita
by Dr. Sarah D. Oktay
Managing Director UMass Boston Nantucket Field Station
This is the full version of the article that appeared in the print version of Yesterday's Island.
We live with it every day. Almost every plant on island has some tolerance to it. Many of our plants can’t live without it. Could it be high priced fertilizers? Water? Sunlight? Well, two of those are necessary, but what we are talking about today is salt or salinity tolerance and how excess salt spray can affect plants after a “dry” tropical storm. Fortunately, here on Nantucket, Hurricane Irene was not the menace originally predicted. Folks on the mainland from Vermont to Virginia bore the brunt of the storm’s wrath from extremely high rainfall and driving winds. But the island did take a beating to some of its plant life in the form of salt spray damage. It is hard to imagine what is normally a gentle, constant companion on island can quickly accumulate in leaf burning amounts. The majority of plants on Nantucket are typically relatively well adapted to salt spray. They have little choice on a 50 square mile island 26 miles from the mainland. The most noticeable and almost shocking consequence from the Hurricane/Tropical storm was the preponderance of damage to plants on the south shore. You can track the strength and direction of the prevailing winds by walking in a straight line from Cisco or Smooth Hummocks to the north.
Megan Griffiths of Tufts University found that although it was anecdotally understood that salt spray damage from a tropical cyclonic storm could be pretty severe, especially if little rainfall accompanied it, few scientists had gone to the trouble to quantify the effect much less evaluate the time it takes for plants to rebound. Hurricanes like Irene are a classic example (when it came into range of Nantucket) of an encounter with the “dry side” of a tropical storm which, in this case, is the west side of a north-tracking storm. Without large amounts of rainfall, leaves do not have an opportunity to shed the salt before it begins to affect the tissue, causing browning, “burning”, and eventually necrosis (cell or tissue death). Her abstract summarizes a series of measurements on coastal heathland species: “Tropical cyclonic storm systems can have profound impacts on coastal plant communities both through direct mechanical damage and indirect factors, such as flooding or salt spray. Storms with high wind and low rainfall are especially likely to cause high salt spray accumulation on plants growing in close proximity to the ocean. I measured salt spray accumulation on a common coastal heathland plant species, Myricapensylvanica, during normal growing season conditions and following Tropical Storm Floyd. At both sampling times, salt spray accumulation was highest in areas closest to the ocean and salt decreased as distance from the ocean increased. Salt spray accumulation on leaves following the tropical storm was twice the salt spray accumulation during normal growing-season conditions. I also found higher necrosis on leaves following the tropical storm, particularly at distances farther from the ocean. These results suggest that even minor cyclonic storms could have an impact on coastal plants in New England through salt spray damage. More at http://www.jstor.org/pss/30138406 (accessed Sept 10th, 2011). The most susceptible plants were those further from shore who had sequestered themselves in a zone where salt spray is less common or in lower concentrations.
Salt from sea spray acts very differently depending on the time of year it occurs and whether it is concentrated in soil or on the leaves of plants. In spring, plants are much more vulnerable to salt spray. In fall, many trees have survived significant storms because they were in the process of dropping their leaves and typically the evergreens might fare worse during those events. Rainfall is key. If the soil is not saturated by salt water or it is presaturated with fresh water from rain or rinsed out sufficiently afterwards, most plants can bounce back. Many gardeners are able to treat salt soaked soil with gypsum or limestone to counteract the salt. Fertilizers are a bad thing to add because most of those contain salt.
This site http://www2.sunysuffolk.edu/mandias/38hurricane/damage_caused.html (accessed Sept 9th, 2011) describes a harrowing record of lives lost and buildings and landscapes destroyed by the hurricane better known as the Long Island Express. “Salt spray from wind-blown sea water and mixed rain water also had the effect of browning trees that did survive. Weeks later these trees were dead. One can still find many downed trees throughout eastern Long Island's forest that are a direct result of this great hurricane. More recently, a study of the Buzzard's Bay coastal region revealed that 50% of the salt-sensitive White Pines were killed by salt spray from Hurricane Bob in 1991 (USGS). In 1938, Long Island salt marshes were inundated with tons of overwash (sand brought over the dune into marshland areas) that prevented the marsh grasses from growing back. This effectively decreased the area of the salt marsh for years.”
This article published via the Arnold Arboretum at Harvard University (Salt water injury of woody plants resulting from the hurricane of September 21, 1938; Bulletin of Popular Information Series 4 Vol. VII November 3, 1939, Number 10- http://arnoldia.arboretum.harvard.edu/pdf/articles/1305.pdf) paints a much rosier picture of the recovery rate of plants after a major storm. The authors systematically observed various plants in the area to evaluate how quickly the plants would bounce back after exposure to hurricane force winds and salt in the Woods hole, Falmouth, Newport, Rhode Island and the north shore of Massachusetts. I especially like this extremely optimistic (and misguided quote) “Fortunately, with hurricanes in the east spaced 100 years apart, it is not necessary that the fear of another in the immediate future should govern present seashore planting”. One of the many plants that survived relatively unscathed was the Japanese pitch pines mentioned last week and the currently blooming Baccharis halimifolia (discussed more below). Overall, the authors were extremely impressed by the ability of many plants (each divided into hardiness after salt exposure) to recover. Botanists associated with Arnold Arboretum did the same type of evaluation after hurricane Donna (http://arnoldia.arboretum.harvard.edu/pdf/articles/1571.pdf). Good soil (more organic matter than sand) and warmer winter temperatures helped plants to survive a “good salt dousing”.
It’s hard to believe a storm so severe that even a salt marsh plant has trouble bouncing back. Smooth cordgrass (Spartina alterniflora), dominates the regularly flooded low marsh. Smooth cordgrass is the most abundant salt marsh plant on Nantucket and is responsible for much of a marsh's productivity. Spartina's successful adaptations enable it to live where few other plants could survive. It has narrow, tough blades and special glands that secrete excess salt, enabling it to withstand daily exposure to salt water and higher temperatures. Few animals eat this plant, but many animals and plants live on it or on the marsh surface protected by its roots and stalks. Spartina stalks are thick and are very tough and well anchored by a root system.
From a distance, the low marsh appears to be uniform; however, there are two forms of Spartina. A tall form grows along creek banks, mosquito ditches and closest (typically) to the wettest, most often submerged parts of the salt marsh and can reach heights of 9 feet. A short form of Spartina occurs in interior parts of the low marsh and ranges from 2 to 3 feet in height. In contrast to the low marsh which has one major species of plant, the high marsh contains a mixture of several species including black rush, Juncus gerardii, Spartina patens (salt hay or salt meadow cordgrass), some short-form smooth cordgrass, and glassworts (Salicornia spp.). This high marsh area grades into a marsh-upland border which is a transitional zone between the salt marsh and the maritime shrub community that consist of groundseltree (Baccharis halimifolia), bayberry, poison ivy, seaside lavender, and the shrub Iva frutescens (also called high tide bush and marsh elder, more specifically the Southern Maritime Marsh-elder).
So, to summarize, salt marshes are transitional areas between land and water, occurring along the intertidal shore of estuaries and sounds where salinity (salt content) ranges from near ocean strength (33-35 parts per thousand or ppt) to near fresh ( zero ppt) in upriver marshes. Plants grow in different tidal zones based on their salt tolerance, with the highly-adapted grasses of the Spartina genus growing directly in the water and making up the majority of the marsh, Marsh Elder and Groundsel shrubs in an intermediate zone, and Typha (Cattails) and Phragmites Australis (invasive , difficult to remove,Common Reed,) existing in the much fresher sections of the marsh where fresh water flows in. Nutrients brought in by rain water from the uplands combined with an abundance of decomposing organic matter makes the salt marsh one of the most productive habitats on earth, and an important breeding ground and nursery for salt water fish, shrimp, crabs, and shellfish including mussels and snails.
A large amount of biomass is created and consumed in the average salt marsh. When the Spartina species die they break apart with the help of decomposers, crabs, snails, and wind and waves into small pieces called detritus that fuels the marsh and its animals. In spring and summer, marshes are lush green, highly productive and grow in height. In late fall, the green Spartina begins to turn brown as leaves die and decomposition begins. Water, waves, wind and storms dislodge and break up decaying leaves, and transport them to mud flats and other locations around the marsh. This dead plant matter, or detritus, forms an attachment site for microscopic organisms such as bacteria, fungi and small algae. These organisms colonize the broken bits of plant material and break down portions of the detritus that are not digestible by animals. This occurs best in a “reducing” environment where oxygen concentrations are low and this gives salt marshes their sulfur-y rotten egg smell (from hydrogen sulfide which is released from the muck).
One of my favorite plants on Nantucket is just starting to bloom, and this is a plant that can withstand a lot of salt water stress. It also is the epitome of “truth in advertising”. I am referring to the “high tide plant” or in this case Baccharis halimifolia also known as the Groundsel tree or Salt marsh elder or sometimes the Sea myrtle. There are many different “high tide” shrubs which demarcate the average height of the wintertime high tide. If you look out over Folgers’ Marsh, you’ll see Baccharis and its very similar twin Iva Fructens arrayed around the marsh at the highest wrack line. It is a member of the aster family and Rick Kessler lab up at Umass Boston has been studying the genetic diversity of these plants at the field station for several years.
Groundseltree’s numerous branches emerge from short trunks are covered densely with branchlets. The 6-12 foot deciduous shrub bears gray-green, somewhat lobed, oval leaves which are semi-persistent in the North (evergreen=ish; unlike my house plants). White to green flowers occur in small, dense, terminal clusters. Probably the most significant feature which you’ll be able to see all over Nantucket does the silvery, plume-like achenes (simple dry fruit) which appear in the fall on female plants resemble silvery paintbrushes. Groundsel Bush is the only native eastern species of the aster family reaching tree size. Baccharis is the ancient Greek name (derived from the Roman god of wine and intoxication, Bacchus) of a plant with fragrant roots. The Latin species name means with the leaves of Halimus, an old name for Saltbush, an unrelated shrub (Halide always referring to salts). Tolerant of saltwater spray, this handsome ornamental is one of the few eastern shrubs suitable for planting near the ocean.
http://www.wildflower.org/plants/result.php?id_plant=BAHA More information at http://www.fs.fed.us/database/feis/plants/shrub/bachal/all.html
accessed Sept 11th, 2011. These plants exhibit dioecy, which means the male and female plants are segregated. Male plants generally have longer shoots, more tender leaves, grow faster, and flower and senesce earlier than female plants. It looks a lot like marsh elder (Iva frutescens L.) although B. halimifolia has alternate leaves and I. frutescens has opposite leaves and they have very different flowers. In case you aren’t completely confused, B. halimifolia which we said above is commonly known as "groundsel bush" or groundsel tree, is in the same family as the true groundsels, Senecio.
One last, somewhat random, but encouraging note from the site above on the Long Island Express and all the heartache it brought to the country. One of the few saving graces for storms like this (and hopefully some solace for those suffering from Irene) is that the repair and recovery efforts can create jobs. A quote from the article: “One positive economic outcome of the 1938 Hurricane was that it effectively ended the unemployment experienced near the end of The Great Depression. At that time most people were out of work and would gladly work for the standard wage of $2 per day. Because so much damage had occurred to homes and buildings and so many trees were blocking roadways, thousands of people flocked to Long Island in search of clean-up work and repair. In fact, more than 2,700 men were brought into New York and New England by Bell Systems just to repair the downed phone lines."
Here’s hoping you and yours are safe. If you are in town this Fall and especially this Saturday, come to the kick-off event for Nantucket Family Adventure from 12-2 on Saturday September 17th at the UMass Boston Nantucket Field Station 180 Polpis Road. We’ll have games and will hand out nature journals for participating families to fill in as they explore the island over the next few weeks. This is a fun and free event sponsored by all the island’s conservation, science and education groups working together to provide some fun for fall. Hope to see you there, call 508-228-5268 for more information.