| Autor: |
Sandoval-Gil, Jose, Alexandre, Ana, Santos, Rui, Camacho-Ibar, Víctor |
| Předmět: |
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| Zdroj: |
Estuaries & Coasts; Nov2016, Vol. 39 Issue 6, p1694-1708, 15p |
| Abstrakt: |
Oyster farming in estuaries and coastal lagoons frequently overlaps with the distribution of seagrass meadows, yet there are few studies on how this aquaculture practice affects seagrass physiology. We compared in situ nitrogen uptake and the productivity of Zostera marina shoots growing near off-bottom longlines and at a site not affected by oyster farming in San Quintín Bay, a coastal lagoon in Baja California, Mexico. We used benthic chambers to measure leaf NH uptake capacities by pulse labeling with NH and plant photosynthesis and respiration. The internal N resorption/recycling was measured in shoots 2 weeks after incubations. The natural isotopic composition of eelgrass tissues and vegetative descriptors were also examined. Plants growing at the oyster farming site showed a higher leaf NH uptake rate (33.1 mmol NH m day) relative to those not exposed to oyster cultures (25.6 mmol NH m day). We calculated that an eelgrass meadow of 15-16 ha (which represents only about 3-4 % of the subtidal eelgrass meadow cover in the western arm of the lagoon) can potentially incorporate the total amount of NH excreted by oysters (∼5.2 × 10 mmol NH day). This highlights the potential of eelgrass to act as a natural biofilter for the NH produced by oyster farming. Shoots exposed to oysters were more efficient in re-utilizing the internal N into the growth of new leaf tissues or to translocate it to belowground tissues. Photosynthetic rates were greater in shoots exposed to oysters, which is consistent with higher NH uptake and less negative δC values. Vegetative production (shoot size, leaf growth) was also higher in these shoots. Aboveground/belowground biomass ratio was lower in eelgrass beds not directly influenced by oyster farms, likely related to the higher investment in belowground biomass to incorporate sedimentary nutrients. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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