Macroalgae in MD's Coastal Bays
Macroalgae appear in a variety of colors and forms. They are divided into the three groupings- red, brown and green -based on pigments (e.g. color of the plant). They can appear as small "fur like clumps," moderate-sized branched specimens, or large leaf-type structures.
Most people in the United States ingest red or brown algae products everyday in chocolate milk, toothpaste, candy, cosmetics, ice creams, salad dressing, and many other household and industrial products (McCoy, 1987). Macroalgae are rich in protein, carbohydrates, amino acids, trace elements, and vitamins (Waaland, 1981).
Below is some background information on the genera of macroalgae (or seaweeds) found in the Maryland Coastal Bays during 2001 and 2002.
Red Algae or Rhodophytes
The red algae had the greatest richness with eight genera identified. Red algae are the most diverse group of macroalgae inhabiting, both temperate and cold marine waters. Three genera, Ceramium, Agardhiella and Gracilaria, are prominent in the mid-Atlantic. Red algae are often commercially raised and harvested for their agar and carrageenans which are used in the food, cosmetic and medical industry.
Moul (1958) identified both Agardhiela tenera and Gracilaria foliifera in Chincoteague Bay and two species of Gracilaria have been reported from Virginia (Humm, 1979), G. foliifera and G. verrucosa. Likewise, Agardhiella tenera was identified in Delaware (Timmons and Price 1996). Based on field observations, it is likely that both genera are currently present in Maryland.
Gracilaria tikvahiae is often found in areas undergoing eutrophication (Peckol et al. 1994). In Waquoit Bay, Massachusetts, this species along with Cladophora vagabunda are found in thick, extensive unattached mats contributing to 95% of standing biomass of the Bay (Peckol et al. 1994). Both show rapid growth and Nitrogen uptake rates (Peckol et al. 1994), have high tissue Nitrogen storage capacity (Lapointe and Duke 1984), and tolerate indirect effects of Nitrogen loading, e.g. anoxia and elevated Nitrogen (Peckol and Rivers 1995). Thus these macroalgae have a number of physiological traits contributing to their competitive superiority in eutrophic systems (Peckol and Rivers 1995). A study conducted in Logan River and Southern Moreton Bay, Southeastern Queensland, Australia found that tissue of Gracilaria spp. and other macroalgae correlated with dissolved inorganic nitrogen (Horrocks et al 1995). An in vitro study by (Peckol and Rivers 1995) found that G. tikvahiae exhibited higher growth rates under photon flux density, light saturation, and consistently showed greater growth when grown in a single species rather than mixed species when compared to Cladophora vagabunda. Gracilaria tikvahiae grows in largely shallow areas (less than 1 m) in Waquoit Bay, Massachusetts.
Polysiphonia is a common genus with numerous species varying in form and size (Carr 2003; Schneider and Searles, 1991). Also known as Pod Weeds, plants are found on the entire east coast of North America as well as on the west coast and other sites throughout the world (Carr 2003; Gosner 1978; Schneider and Searles, 1991). Polysiphonia can be epiphytic, and is often found growing on rocks, seawalls, pilings, jetties, and floating buoys (Parmentier 1999; Johannesson et al. 2000; Gosner 1978; Schneider and Searles, 1991). At times, Polysiphonia can also be found drifting free (Gosner 1978). Polysiphonia can grow in many environments ranging from the open coast to protected bays and sounds, mainly in shallow subtidal areas, but can be found present in the lower intertidal zone (Gosner 1978; Schneider and Searles, 1991). Some species of Polysiphonia are annuals while some are perennial, with others reaching peak size during the months of November through March (Gosner 1978; Schneider and Searles, 1991). Because Polysiphonia has a rapid growth rate and is an opportunist, it can displace native species and become very abundant (Maggs 2003). Polysiphonia is also very tolerant to temperature changes, which influences its success in spread and distribution (Maggs 2003). Polysiphonia can also be a fouling agent because it is abundant in marinas on artificial structures (Maggs 2003).
Species of Champia, or Barrel Weed, occur in tropical to temperate waters and are mainly present in the summer to early fall, but towards the south can be found year round (Scowcroft 2003; Orfanidis and Breeman 1999; Gosner 1978). Also known as Barrel Weeds, the plants are often epiphytic on smaller algae but can also be found drifting and washed ashore (Tempera et al 2003; Gosner 1978). The plants are attached by small discoid holdfasts, and the plants can be erect to lying flat (Schneider and Searles 1991). Champia is mainly found in lower intertidal pools and subtidal in generally quiet water (Tempera et al 2003; Gosner 1978).
There are numerous species of Ceramium or Banded Weeds and they are all small plants, which are epiphytic, epizoic, or found growing on rocks or other substrates (Lobban 2001; Johannesson et al 2000; South and Skelton 2000; Gosner 1978; Schneider and Searles 1991). The plants are attached to these substrates by basal rhizoidal holdfasts (Schneider and Searles 1991). Ceramium is found mainly in brackish water along the entire east coast from the lower intertidal zone to subtidal in shallow water (Gosner 1978; Schneider and Searles 1991). Most species of Ceramium grow best in summer to early fall (Gosner 1978). Ceramium plants produce chemicals that are not palatable in order to reduce consumption by herbivores (Lobban 2001).
Spyridia is found at marshes, jetties, and offshore from Cape Cod to the tropics (Gosner 1978; Schneider and Searles 1991). The plants are epiphytic and are chiefly prevalent in the summer (Gosner 1978; Schneider and Searles 1991). Spyridia can accumulate dissolved nitrogen, but the accumulated nitrogen pools decline quickly when ambient levels decline (93% in four days) (McGlathery 1992). A reduction in nitrogen leads to a reduction in pigment in the plants, therefore, less photosynthesis occurs causing the plants to become severely bleached (McGlathery 1992). When ambient nutrient levels decrease, both nitrogen and phosphorus levels decrease in Spyridia, at the same rate maintaining the nitrogen/phosphorus ratio. Macroalgae with rapid nutrient uptake such as Spyridia are dominant in eutrophic environments with high nutrient supplies, but tend to be absent from low nutrient habitats because the macroalgae can not acquire sufficient nutrients to maintain metabolic needs of maintenance and growth (McGlathery 1992).
Naturalized from Europe (Gosner 1978) Hypnea sp. or Hooked Weeds, are typically perennials with distinctive hooked ends. They can be found growing in the subtidals but are more commonly found washed ashore (Gosner 1978).Also known as pod weeds, the four species of Chondria are difficult to differentiate (Gosner 1978). C. baileyana is epiphytic on rockweed, eelgrass and the like but is sometimes found drifting (Gosner 1978). Dominant in the lower intertidal to subtidal zone and during the summer (Gosner 1978).
Green Algae or Chlorophytes
Six genera of green algae (Chlorophyta) have been documented in the MD Coastal Bays including: Ulva, Chaetomorpha, Enteromorpha, Cladophora, Bryopsis and Codium. Of these, Ulva spp. was the most prevalent, occurring at 10% of all stations sampled, 13% in the spring, 5% in the summer, 9% in fall and 11% in winter. Ulva spp. was generally distributed through out the bays, however, it was most consistently present in the northern bays and Sinepuxent Bay.
Ulva is initially attached, but in later stages of life is free drifting (Gosner 1978). The holdfast is perennial, and the blade of Ulva is annual (Gosner 1978). Ulva ranges from the sub-arctic to the tropics (Gosner 1978). Ulva is tolerant to a wide range of temperatures, and can avoid dessication at low tides (Stewart 1996). It is often epiphytic on other species of algae, and is found in all intertidal zones (Stewart 1996). Ulva is a bright green in color and has broad, flat blades with ruffled edges, and can grow up to 3 feet (Stewart 1996). Because of its lettuce like appearance, it is commonly called sea lettuce. Ulva can be found in a variety of places ranging from exposed rocks to brackish pools (Gosner 1978). When found in areas that are enclosed or semi-enclosed, and have little mixing, Ulva makes up a large portion of the drift algae which can smother benthic communities below (Gosner 1978).
Ulva is likely to proliferate where nutrients are high, wave-shearing forces are low and herbivory is reduced (Kirby 2001). However Ulva is tolerant of stressful conditions, and is often an indicator or freshwater input or pollution (Kirby 2001). In fact Ulva needs to be in nitrogen rich environments, and when concentrations are particularly high, Ulva can take up more than most species and thus grows rapidly (Kirby 2001). Ulva has very little ability to store nitrogen in its tissues (Durkee et al. 2003), and it thrives in brackish water with organic enrichment (Guiry 2003). It is also a good bio-indicator of metal contaminations such as Mn, Fe, Cu, Zn, and Pb, because metals interfere with Ulva’s reproduction (Kirby 2001). Ulva contains a high concentration of pigments and therefore can absorb almost all wavelengths of light, and thus does better in shallow water (Gosner 1978). “While Ulva…is well suited for conditions that require rapid growth, high nutrient uptake and high biomass production in low light, it is out competed by species that are more rugged and have better abilities to store nutrients” (Durkee et al 1999).
Chaetomorpha is an un-branched filamentous algae that has a coarse and wiry, even bead-like appearance (Gosner 1978). It is more than 1/8 inch thick, and grows to be about a foot or more long and is typically found in drifting tangles (Gosner 1978) that resemble tangled fishing line. Chaetomorpha is blue-green in color (Gosner 1978) and attaches in pools or on lower intertidal rocks. Some species can be found from the Artic to Cape Cod, others are found along the whole Atlantic coast (Gosner 1978). Chaetomorpha is light dependant, and with more irradiance, Chaetomorpha utilizes more nutrients in a system (Krause-Jensen et al 1996). In the light, Chaetomorpha reduces the flux of nutrients in the water column, and with increased irradiance and water temperature Chaetomorpha can consume more oxygen than it produces (Krause-Jensen et al 1996). Additionally, water turbulence can benefit Chaetomorpha by increasing the amounts of NH4+ , NO3- and PO4- that it uses.
Enteromorpha is a tubular plant, hence the common name Hollow Green Weed, that can be branched or un-branched, and is sometimes flattened (Gosner 1978). It is grass green in color, and larger specimens have air bubbles in the thallus (Gosner 1978). Enteromorpha can be less than an inch wide and more than a foot long (Gosner 1978). Different species have different growing seasons, where E.linza is found in winter and spring only, E. intestinalis is found year round, and most other speceis are spring-summer annuals (Gosner 1978).
Enteromorpha is found from the artic to the Carolinas in a variety of habitats (Gosner 1978). It is commonly attached to rocks, shells and wood in the lower intertidal zones, is found in mud flats, and can be drifting free or epiphytic (Gosner 1978). Enteromorpha is often inhabits brackish water areas (where there is appreciable fresh water run off) and wet areas of the splash zones (Bud and Pizzola 2002). Enteromorpha also has a wide tolerance for varying and greatly reduced salinities (Gosner 1978). The genera’s abundance is governed by the availability of nirogen (Inter-Research 2001). In fact, Enteromorpha is being investigated for its uses as treatment of secondary municipal sewage and biomass, for energy conservation (Bud and Pizzola 2002). Enteromorpha is not sensitive to heavy metal contaminations, but is highly sensitive to hydrocarbon contamination, however it is able to recover from this stressor (Bud and Pizzola 2002)
Cladophora is a branched filamentous alga that can grow up to two feet long. Its thickness ranges from hair-like to about the thickness of light sewing thread (Gosner 1978). Cladophora is bright to rich green in color and is attached intertidally and subtidally at shallow depths, or can be free floating in a greenish mist (Gosner 1978). Cladophora can sustain a significant amount of hydrodynamic force (Nakano 1996). It is sometimes epiphytic and is abundant along the entire Atlantic coast (Gosner 1978).
Light is essential for Cladophora growth, and thus it is usually found in shallow water (Lynne 2000). It is a perennial, growing in the summer and fall when the water temperatures are warmer (Lynne 2000). The biomass of Cladophora is determined by factors such as substrate, high nutrients and light availability (Shelton et al 1999). Cladophora can accumulate contaminates from the water even at low concentrations, and is thus an excellent bio-indicator of chronically low levels of contamination (St. Claire River Remedial Action Plan 2003). Cladophora is found in both fresh and salt waters and is a benthic opportunistic settler (St. Claire River Remedial Action Plan 2003).
Bryopsis has a delicately bushy appearance with regular branching, and grows up to 4 inches. It grows in fernlike tufts and has a light green color, thus its common name green sea fern (Gosner 1978). It ranges from Cape Cod to Florida, and is a perennial in the south, and an annual northward (Gosner 1978). Bryopsis is found in tide pools and on wood in fairly quiet water at shallow depths (Gosner 1978). It is most plentiful during spring and summer (Rice 2003), its breeding season. It is limited in growth by high pH.
Codium has a coarsely bushy appearance and often branches in regular y-shaped forks (Gosner 1978). Codium has thick, rope-like or spongy branches, and grows to 3 feet (Gosner 1978). Its common name is Green Fleece, and it has a dark green color bleaching to yellowish (Gosner 1978). Codium is described as perennial, biennial or pseudo-perennial, and often lives for several years (Gosner 1978). Biomass for Codium is greatest from August to October, and least from March to April (Kennedy 1997). Codium can be found from Cape Cod to Barnegat Bay, however some species are tropical (Gosner 1978). Codium is widely distributed in the lower intertidal zones (Tyson 1996) and is usually found in dense patches in the shallow waters of sounds and bays (Gosner 1978). It has a basal holdfast, and can use any firm, stationary object for attachment such as rocks and oyster shells, but it is also a good substrate for other epiphytic species (Kennedy 1997). Accidentally introduced from Europe or the North Pacific in 1957, this genus can be disruptive to ecosystems displacing native algal species and smothering shellfish (Gosner 1978; Kennedy 1997).Three important factors that influence Codium’s growth include, temperature, irradiance and salinity. Optimal temperature for Codium is 24°C, although it can grow from 10-30°C (Kennedy 1997). Codium grows best at a minimal irradiance of 28uE per meter squared per second (Kennedy 1997). However Codium can absorb virtually all wavelengths of light, attributing to its dark green almost black color (Kennedy 1997). Codium can grow at salinities ranging from 6-48ppt, with optimal growth occurring between 24-30ppt (Kennedy 1997). When nitrogen is limited, Codium can appear sickly and bleached with a coat of fine hairs, that increase the absorptive area (Kennedy 1997). It can utilize nitrogen in many forms such as nitrate, nitrite, ammonium and urea (Kennedy 1997) but only in low concentrations (Tyson 1996).
Brown Algae or Phaeophytes
Brown algae are usually marine (abundant in cold water) and many species inhabit the intertidal zone. Brown algae (Phaeophytes) in the coastal bays were represented by four genera: Desmarestia, Ectocarpus, Stilophora and Sphaerotrichia. Algins, which are used to produced rubber, textiles and food thickners for soups, mayonnaise, sauces, and sausage casings, are a major constiutent of all brown algae (McCay, 1987). The Brown algae in the MD Coastal Bays were represented by four genera: Desmarestia, Ectocarpus, Stilophora and Sphaerotrichia. Desmarestia spp. and Ectocarpus spp. are two genera that are very similar in appearance and difficult to differentiate in the field. For the purposes of our study, we combined them into a complex referred to as the Des/Ect spp. complex. [Note: Schneider and Searles (1991) classify many of the Ectocarpus sp. as Hincksia sp.]
Ectocarpus is common in the oceans throughout the world and is present on the entire east coast (Gosner 1978; Carr 2003). It can be found in various forms growing as an epiphyte, forming soft beards on large plants and rocks, or as free floating entangled mats in sheltered waters (Schneider and Searles 1991; Scowcroft 2003, Carr 2003). Ectocarpus is common year round and is often found on jetties and in sounds (Schneider and Searles 1991; Scowcroft 2003). It has become tolerant to metal pollution, which commonly surrounds ports and docks (Cardillo et al 1999).
The cells of Desmarestia, or Sour Weed, contain sulfate ions, and when disrupted, release these ions that then interact with seawater to produce sulfuric acid (Scowcroft 2003). This serves as protection against predation by most creatures.
Stilophora rhizodes is one species that is common along the eastern shore of Virginia, in the winter and spring. It’s distribution ranges from Florida to Prince Edward Island where it is commonly found in the summer. It can appear as an epiphyte or free drifting. It is pale to yellowish brown with thin branches that can grow up to one foot in length. Stilophora is commonly found in shallow, quiet waters (Gosner 1978).
Sphaerotrichia spp is similar to Stilophora, but is more slender and can grow up to 20 inches in length. It is epiphytic and is distributed from New Jersey to Labrador (Gosner 1978).
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