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Quantity and quality of particulate organic matter controls bacterial production in the Columbia River estuary
Author(s) -
Crump Byron C.,
Fine Lindy M.,
Fortunato Caroline S.,
Herfort Lydie,
Needoba Joseph A.,
Murdock Sheryl,
Prahl Fredrick G.
Publication year - 2017
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.1002/lno.10601
Subject(s) - estuary , particulates , environmental science , turbidity , organic matter , biogeochemical cycle , settling , phytoplankton , oceanography , hydrology (agriculture) , water column , chlorophyll a , environmental chemistry , ecology , nutrient , geology , chemistry , biology , environmental engineering , biochemistry , geotechnical engineering
Abstract Estuaries function as “bioreactors” for fluvial materials in which microbial, biogeochemical, and ecological processes transform organic matter and nutrients prior to export to coastal oceans. The impact of estuarine bioreactors is linked to the bioavailability and residence time of fluvial material, and to rates of microbial activity. In the Columbia River estuary, water residence time is short (approximately 2 d), but particle residence time is extended by estuarine turbidity maxima (ETM). To investigate relationships between organic matter and microbial activity, samples were collected in spring and fall 2012 and summer 2013, and ETM particles were fractionated by settling velocity using an Owen‐style settling column. Data were also analyzed from 16 other sampling campaigns conducted in 1990–2009. The composition of suspended particulate matter shifted seasonally following the spring freshet and river phytoplankton bloom with decreasing organic content, increasing C/N ratio, and an increasing contribution of autochthonous particulate organic matter (POM) produced in four shallow lateral bays (based on del‐PO 13 C and pigment ratios). Heterotrophic bacterial production responded to seasonal changes in POM and correlated most strongly with estimates of labile particulate nitrogen during any particular season, and with the riverine flux of chlorophyll a (Chl a ) across all seasons. Regression models suggest that labile particulate nitrogen and bacterial production can be predicted from sensor‐based measurements including turbidity, salinity, and temperature in the estuary and Chl a in the river. These results demonstrate that heterotrophic activity in the Columbia River estuary is controlled by POM lability, and by the degree to which ETM retain and concentrate POM.