Spatial and temporal variation in C:N:P ratios, delta15N, and delta13C of eelgrass Zostera marina as indicators of ecosystem processes, Tomales Bay, California, USA

Abstract

The nutr~ent content, 6I5N, and F13C of seagrasses in Tomales Bay (California. USA) vary in both space and time. The variations In these measurements were not random, but followed spatial and seasonal patterns that provide ins~ght into the sources and processing of nutrients In the Tomales Bay ecosystem. Wide ranges of carbon, nitrogen, and phosphorus content of green leaves of Zostera marina were found in 72 samples collected over the 2 yr of sampling. Carbon content varied from 29.0 to 40.9% of dry weight, nitrogen from 1.13 to 3.79*,, and phosphorus from 0.11 to 0.90%. Stable isotopic composition was variable as well: the mean 6"N for all samples collected was 9.7 + 0.3% with a range of 6.2%0. Carbon so topic content had a range of 7 5lV&, with a mean 613C of -9,6 + 0.2"/00. There was a strong spatial trend in the N content, but not the P content, of Z. marina leaves from Tomales Bay. The C:N ratio was around 15 near the mouth of the bay and increased linearly with distance into the bay to -25 near the head of the bay; there was a concomitant pattern of increasing 6I5N of seagrass leaves, from 7 % near the mouth of the bay to near 12%0 at the head of the bay. The spatial pattern in N content was only present during summer months, but the spatial pattern in stable isotopic composition was present in both summer and winter. The patterns in the N and 6"N content of the seagrasses indicate the importance of denitrification in the C and N cycles in Tomales Bay. The analysls of patterns in variation of elemental content and isotopic composition of seagrasses is a powerful tool for investigating ecosystem-scale processes in coastal marine systems. Similar analyses of seagrasses from less well studied ecosystems should provide data to generate hypotheses about spatial and temporal variation in processes in these other systems.

Combined nutrient and macroalgae loads lead to response in seagrass indicator properties

“…3A & B). The C content of Z. marina in macroalgae and nutrient loading treatments, and particularly for their combined treatment, was much lower than in the control treatment and literature values taken from Europe (leaves: 34.9-40.3%; root-rhizomes: 33.6-36.0%) (Pedersen and Borum, 1992) and North America (leaves: 29.0-40.9%) (Fourqurean et al, 1997), which might indicate that if the stress was prolonged, it could cause seagrass systems to collapse. Macroalgae cover may reduce the C content of seagrasses for two reasons.…”

“…Physiological variables, such as nitrogen (N) and carbon (C) contents of seagrass tissues, are normally used as fast indicators (days to weeks) of nutrient availability and light reduction (Burkholder et al, 2007;Fourqurean et al, 1992Fourqurean et al, , 1997van Katwijk et al, 2011). Seagrass morphological and structural characteristics (e.g.…”

Growth dynamics of the seagrass, Zostera marina in Jindong Bay on the southern coast of Korea

“…Seagrass, as a primary producer, requires large amounts of inorganic carbon to sustain growth and survival (Duarte 1990, Fourqurean et al 1997, Lee and Dunton 1999. In contrast to terrestrial plants, seagrasses obtain their carbon from seawater, which has high inorganic carbon concentrations (Sand-Jensen 1977).…”

Effects of acidification in multiple stable isotope analyses

“…Nevertheless, this method is used in many recent benthic studies with several variations concerning acid concentration and duration of the bathing in acid (Marguillier et al 1997, Kharlamenko et al 2001, Moncreiff and Sullivan 2001, Fredriksen 2003, Kang et al 2003. Some studies totally dispense with acidification (Fourqurean et al 1997, Jennings et al 1997, Loneragan et al 1997, Connolly et al 1995) and a few studies used an in situ acidification procedure (Deegan andGarritt 1997, Herman et al 2000). Here, the pulverized samples were acidified with a small amount of relative high concentrated HCl.…”