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Effect of macrozoobenthos on two‐dimensional small‐scale heterogeneity of pore waterphosphorus concentrations in lake sediments: A laboratory study
Author(s) -
Lewandowski Jörg,
Hupfer Michael
Publication year - 2005
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 - 10.4319/lo.2005.50.4.1106
Subject(s) - mesocosm , pore water pressure , sediment , environmental chemistry , sediment–water interface , water column , redox , phosphorus , nitrate , diagenesis , chemistry , environmental science , ecology , geology , mineralogy , ecosystem , oceanography , biology , geomorphology , geotechnical engineering , organic chemistry
We used mesocosms equipped with two‐dimensional (2D) pore water samplers (24 rows X 24 columns, 9‐mm spatial resolution) to resolve and quantify some of the complex spatial patterns in diagenetic reactions produced by irrigated biogenic structures. The mesocosms were filled with an organic‐, iron‐, and phosphorus‐rich sediment, and chironomids and oligochaetes were added in high densities to three of six mesocosms; the other three mesocosms served as controls. In the mesocosms without macrozoobenthos, a classic redox zonation developed. In the mesocosms with macrozoobenthos, profiles of redox‐sensitive dissolved species were less steep in the vicinity of the sediment‐water interface, and more irregular throughout the sediment, than in the mesocosms without macrozoobenthos. Furthermore, pore water P concentrations were decreased overall and showed much more small‐scale 2D heterogeneity in the mesocosms with macrozoobenthos than in the controls. A comparison of the calculated heterogeneity indices of pore water P concentrations (the ratio of horizontal to vertical flux components) of this laboratory study with in situ‐determined indices of previous studies indicates that the presence of macrozoobenthos is the major factor causing heterogeneity. A conceptual model of the effects of macrozoobenthos on biogeochemistry along with pore water and sediment analysis showed a close coupling of P cycling with iron and sulfur cycling. This led to the conclusion that pore water P concentrations and heterogeneity were mainly redox‐controlled by association of P with iron oxyhydroxides precipitating along oxidized burrow walls, and not a consequence of mineralization processes occurring in organic‐rich “hot spots” of increased P turnover. Decreased P release rates accompanied addition of macrozoobenthos and indicated that redox control of P release by iron oxyhydroxide precipitation and dissolution was of major importance.