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This photograph was taken on the intertidal mudflats at Lindisfarne, Northumberland, UK today. It was about 40m from the shoreline at low tide. Is the green plant a species of zostera? Can anyone help with the identification?
It certainly looks like a Zostera species. The ones that appear in the UK are Zostera angustifolia, Zostera noltii, and Zostera marina. Its hard to tell exactly which species this one is without size information and knowing the conditions of the bay. Z. marina has the broadest leaves at around 5 - 10 mm, whilst Z. angustifolia has leaves just 2 - 3 mm broad. Is 40m around the mid-water mark? If so I would hazard a guess this is Z. angustifolia. Z. marina tends to stick to areas permanently covered by the sea (sub-littoral) whilst Z. noltii likes much more sheltered conditions than the middle of the bay, tending to stick to the upper shore.
Hope that helps!
Can be confused with other species in the genus Zostera. Z. muelleri has a rounded notched leaf tip, compared with Z. nigricaulis with rounded tips. Z. muelleri has 2-4 leaves per stem, compared with 5-12 leaves on Z. nigricaulis. Z. muelleri lacks the long thin stem on Z. nigricaulis.
Another species from the genus, Zostera tasmanica, can be distinguished by the absence of a wiry, dark brown stem and presence of pointed leaf tips.
Main information sources:
Womersley, H.B.S., (1984-2003). The Marine Benthic Flora of Southern Australia. Part 1-3d. Govt. Printer, South Australia.
Baldock, R.N. 2010. Algae Revealed. South Australian State Herbarium. Website.
Linear leaves with 3 longitudinal veins (1 is prominent). Two to four leaves per shoot. Apex of leaf is rounded and notched. Shoots are short (1-2 cm) and arise from rhizome nodes. Roots occur at nodes of rhizomes. Leaves medium green. Up to 10 cm long (leaves), can be to 60 cm when permanently submerged.
This species is sensitive to increased nutrient levels in the sediment. It flowers and fruits between October and March. Each plant is both male and female (monecious). This and other species of seagrass are important habitat for many invertebrates, fish and algae. They also provide carbon fixation and are impacted by physical disturbance, pollutants, sedimentation and changes in sea level.
Soft sediments, intertidal and shallow subtidal including lagoons and estuaries, sheltered waters, to depth of 1 m.
This study was carried out as part of the Zostera Experimental Network, ZEN 2015–2018 (NSF award OCE-1336206 to J. E. Duffy). We acknowledge the following people for participating in field sampling: J. K. Baum, M. Björk, K. Boyer, D. Chin, L. Chalifour, S. Cimon, M. Cusson, M. Dahl, D. Deyanova, J. S. Eklöf, J. K. Geyer, J. N. Griffin, M. Gullström, C. M. Hereu, M. Hori, K. A. Hovel, A. R. Hughes, P. Jorgensen, S. Kiriakopolos, M. Nakaoka, M. I. O'Connor, B. Peterson, K. Reiss, P. L. Reynolds, F. Rossi, J. Ruesink, R. Santos, J. J. Stachowicz, F. Tomas, K.-S. Lee and R. K. F. Unsworth.
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Characterization of the mycobiome of the seagrass, Zostera marina, reveals putative associations with marine chytrids
Seagrasses are globally distributed marine flowering plants that are foundation species in coastal ecosystems. Seagrass beds play essential roles as habitats and hatcheries, in nutrient cycling and in protecting the coastline from erosion. Although many studies have focused on seagrass ecology, only a limited number have investigated their associated fungi. In terrestrial systems, fungi can have beneficial and detrimental effects on plant fitness. However, not much is known about marine fungi and even less is known about seagrass associated fungi. Here we used culture-independent sequencing of the ribosomal internal transcribed spacer (ITS) region to characterize the taxonomic diversity of fungi associated with the seagrass, Zostera marina. We sampled from two Z. marina beds in Bodega Bay over three time points to investigate fungal diversity within and between plants. Our results indicate that there are many fungal taxa for which a taxonomic assignment cannot be made living on and inside Z. marina leaves, roots and rhizomes and that these plant tissues harbor distinct fungal communities. The most prevalent ITS amplicon sequence variant (ASV) associated with Z. marina leaves was classified as fungal, but could not initially be assigned to a fungal phylum. We then used PCR with a primer targeting unique regions of the ITS2 region of this ASV and an existing primer for the fungal 28S rRNA gene to amplify part of the 28S rRNA gene region and link it to this ASV. Sequencing and phylogenetic analysis of the resulting partial 28S rRNA gene revealed that the organism that this ASV comes from is a member of Novel Clade SW-I in the order Lobulomycetales in the phylum Chytridiomycota. This clade includes known parasites of freshwater diatoms and algae and it is possible this chytrid is directly infecting Z. marina leaf tissues. This work highlights a need for further studies focusing on marine fungi and the potential importance of these understudied communities to the larger seagrass ecosystem.
The submersed marine angiosperm, eelgrass (Zostera marina L.), resides in a habitat that is characteristically harsh and dynamic. This environment is often described as light-limited from extended periods of light attenuation (Backman and Barilotti, 1976) carbon-limited due to decreased availability of dissolved inorganic carbon (i.e., CO2, HCO3 − , and CO3 − 2 ) in aqueous solutions (Goldman and Graham, 1981, Turpin et al., 1985, Levavasseur et al., 1991) and/or nutrient-limited (both N and P Short, 1983, Murray et al., 1992, van Lent et al., 1995, Udy and Dennison, 1997, Peralta et al., 2003 but see Zimmerman et al., 1987). Reduction of photosynthetically active radiation (PAR) can occur from various natural and anthropogenic factors. For example, high production of phytoplankton in the water column (overlying water), dense epiphytic algal biofilms on the angiosperm leaves, and/or increased floating and attached macroalgal growth can reduce the light available for photosynthesis (Gallegos et al., 1991, Harlin, 1995, Wear et al., 1999, Johnson et al., 2006). Increased particulate matter from coastal development, erosion, storms, and dredging operations may also severely reduce water clarity (Larkum and West, 1990, Coleman and Burkholder, 1994, Badalamenti et al., 2006, De Falco et al., 2006). Other factors aside from low light also contribute to the harsh environment. Hypoxic or low-oxygen conditions may prevail in surface waters under eutrophic (nutrient over-enriched) conditions, and persistent anoxia is common in water-saturated sediments (Mackin and Swider, 1989, Dauer et al., 1993, Goodman et al., 1995, Peralta et al., 2003). Submersed marine angiosperms such as Z. marina must additionally contend with dynamic changes in salinity from fluctuations in precipitation, evaporation, and increases or decreases in water input from other freshwater sources (Adams and Bate, 1994, Tomasko and Hall, 1999, Thorhaug et al., 2006). Despite these stressful growing conditions, eelgrass meadows are among the most productive natural ecosystems in the world, and they provide habitat that is critically needed by many species of finfish, shellfish, and other aquatic organisms (McRoy, 1974).
Extensive research has been conducted on the ecological physiology of Z. marina, including growth and developmental responses of these plants under various environmental conditions. Such studies have examined the effects of salinity, temperature, and light on photosynthesis and respiration (Biebl and McRoy, 1971, Marsh et al., 1986, Torquemada et al., 2005, Kahn and Durako, 2005), as well as the uptake and assimilation of nutrients from the environment (Roth and Pregnall, 1988, Burkholder et al., 1992, Peralta et al., 2003). Impacts on marine angiosperms from elevated levels of nutrients, especially nitrogen, in coastal waters have received increased attention within the past decade. Most nutrient enrichment occurs from sewage and other anthropogenic sources (Magnien et al., 1992, Mallin et al., 1993), and has been strongly correlated with eelgrass decline (Ferguson et al., 1988, Burkholder et al., 1994, van Katwijk et al., 1997, Brun et al., 2002, Peralta et al., 2003, Touchette et al., 2003).
The mechanism generally invoked for reduced eelgrass survival under cultural eutrophication (nutrient over-enrichment from anthropogenic sources) has been algal turbidity (Morris and Riley, 1993). Increased inorganic nitrogen (Ni, especially NO3 − and NH4 + ) has been shown to stimulate algal overgrowth that shades the underlying seagrass and limits available PAR (Kemp et al., 1983). However, a second mechanism for the decreased survival of Z. marina under water-column nitrate enrichment has been reported (Burkholder et al., 1992, Burkholder et al., 1994, Peralta et al., 2003). In long-term (seasonal) experiments, plants in a warm-temperate region declined under low-level water-column nitrate enrichment (3.5 to 7.0 μM NO3 − Burkholder et al., 1992, Burkholder et al., 1994). The plants appeared intact, but the meristem region at the shoot base had poor structural integrity and crumbled when sampled (Burkholder et al., 1992). The most striking eelgrass declines coincided with an unusually warm spring, thereby suggesting a potential synergism between increased temperature and nitrate. The depressed survival was not mediated by algal-induced light attenuation, and it was hypothesized that a physiological mechanism had contributed to the disappearance of eelgrass under nitrate enrichment.
Eelgrass is believed to have evolved in historically nitrogen-limited waters, and this plant may have maximized its nitrate uptake/assimilation processes during infrequent nitrate pulses (Burkholder et al., 1994). Such response would require reallocation of carbohydrates from storage reserves toward the production of energy and carbon skeletons necessary to reduce nitrate and form amino acids (Turpin, 1991, Touchette and Burkolder, 2000b). However, if high water-column nitrate levels persisted (typical of anthropogenic nutrient enrichment), and if a feedback mechanism was not retained to prevent further uptake, these plants may deplete available carbohydrates to levels where growth was substantially compromised (Burkholder et al., 1992, Burkholder et al., 1994, Peralta et al., 2003). Previous research has shown that as much as 45 to 80% of the N needed during maximum growth periods in seagrass species is assimilated through aboveground (shoot) tissues, even when substantial ammonium pools are available in sediment pore waters (Iizumi and Hattori, 1982, Zimmerman et al., 1987, Lee and Dunton, 1999). Thus, water column is a major source of N, and increased water-column nitrate likely would alter physiological processes involved in carbon and nitrogen metabolism for these plants.
Zostera is believed to have originated during the Tertiary period in the Western North Pacific Ocean (McRoy, 1968 den Hartog, 1970). The seagrass as well as a number of other marine organisms most likely invaded the North Atlantic Ocean through the Bering Strait and the Arctic Ocean during the late Tertiary (Durham and MacNeil, 1967).
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