TY - JOUR
T1 - Ecosystem metabolism of benthic and pelagic zones of a shallow productive estuary: spatio-temporal variability
AU - Stæhr, Peter Anton
AU - Asmala, Eero
AU - Carstensen, Jacob
AU - Krause-Jensen, Dorte
AU - Reader, Heather
PY - 2018
Y1 - 2018
N2 - Long-term deterioration of water quality is known to reduce the importance of benthic ecosystem metabolism in shallow coastal ecosystems, but drivers of spatial and short-term variability in ecosystem metabolism are poorly understood. We addressed this knowledge gap through detailed seasonal measurements of ecosystem metabolism across depth gradients from shallow (2 to 3 m) eelgrass-dominated to deeper (4 to 5 m) muddy regions of a shallow, productive estuary. Combined measurements of gross primary production (GPP), respiration (R) and, by difference, net ecosystem production (NEP) by the open-water diel oxygen technique and in situ chamber incubations showed high importance of shallow eelgrass habitats for metabolism at the system scale. Seasonal variations in GPP, R and NEP increased with light availability and temperature with highest NEP in all habitats during the warm and sunny mid-summer. The shallow eelgrass-dominated and neighboring habitats were seasonally net autotrophic (NEP = 0.54 and 0.31 mg O
2 m
−2 d
−1, respectively), compared to net heterotrophy (NEP = −0.26 mg O
2 m
−2 d
−1) at the deeper muddy site. Detailed studies along depth gradients further confirmed the role of eelgrass as a key driver of spatial differences in ecosystem metabolism across the estuary. Strong northerly winds (>8 m s
−1) caused short-term (<24 h) periods of similar oxygen dynamics and similar apparent productivity in shallow and deeper waters, indicative of efficient lateral mixing, while calm periods (<4 m s
−1) enabled formation of ‘pockets’, i.e. water masses with limited connectivity, which exacerbated the metabolic differences between shallow and deep sites.
AB - Long-term deterioration of water quality is known to reduce the importance of benthic ecosystem metabolism in shallow coastal ecosystems, but drivers of spatial and short-term variability in ecosystem metabolism are poorly understood. We addressed this knowledge gap through detailed seasonal measurements of ecosystem metabolism across depth gradients from shallow (2 to 3 m) eelgrass-dominated to deeper (4 to 5 m) muddy regions of a shallow, productive estuary. Combined measurements of gross primary production (GPP), respiration (R) and, by difference, net ecosystem production (NEP) by the open-water diel oxygen technique and in situ chamber incubations showed high importance of shallow eelgrass habitats for metabolism at the system scale. Seasonal variations in GPP, R and NEP increased with light availability and temperature with highest NEP in all habitats during the warm and sunny mid-summer. The shallow eelgrass-dominated and neighboring habitats were seasonally net autotrophic (NEP = 0.54 and 0.31 mg O
2 m
−2 d
−1, respectively), compared to net heterotrophy (NEP = −0.26 mg O
2 m
−2 d
−1) at the deeper muddy site. Detailed studies along depth gradients further confirmed the role of eelgrass as a key driver of spatial differences in ecosystem metabolism across the estuary. Strong northerly winds (>8 m s
−1) caused short-term (<24 h) periods of similar oxygen dynamics and similar apparent productivity in shallow and deeper waters, indicative of efficient lateral mixing, while calm periods (<4 m s
−1) enabled formation of ‘pockets’, i.e. water masses with limited connectivity, which exacerbated the metabolic differences between shallow and deep sites.
KW - benthic habitat
KW - eelgrass
KW - intra-estuarine heterogeneity
KW - pelagic habitat
KW - temporal variability
UR - http://www.scopus.com/inward/record.url?scp=85051395313&partnerID=8YFLogxK
U2 - 10.3354/meps12697
DO - 10.3354/meps12697
M3 - Journal article
SN - 0171-8630
VL - 601
SP - 15
EP - 32
JO - Marine Ecology Progress Series
JF - Marine Ecology Progress Series
ER -