Abstract
Iron (Fe) is an essential component for marine ecosystems, and it is related to the growth of phytoplankton communities and environmental evolution in coastal area. However, the effect of aquaculture activities on sediment Fe levels is not well studied. Fe levels and grain sizes are determined in two cores (respectively Core C in the culture area and Core A in the control area) in Sishili Bay to reveal the influence of cultivation on sediment Fe levels over an extended period. The sediment Fe levels are distinguished in the upper sections (culture period) but equal in the lower sections (non-culture period) of the two cores. The core C has the same Fe levels as Core A before 1950s (non-culture period). However, the sediment Fe levels of Core C increased during 1950s–1970s (the algae culture period) and decreased after the 1970s (shellfish culture period) compared with Core A, indicating the algae and shellfish culture impose opposite effects on sediment Fe levels. Similarly, sediment grain sizes are observed to be finer during the algae culture period but coarser during the shellfish culture period, and the variation of sediment grain sizes because of culture activities is the important factor affecting sediment Fe levels. The slowing down of ocean current due to algae culture causes finer particles and higher Fe levels in sediment. However, during the shellfish culture period, bio-deposition and re-suspension play major roles in coarsening sediment particles and decreasing sediment Fe levels.
Highlights
Marine culture activities have seen an increase during the last several decades due to the increasing demands for aquaculture products and the need for seafood supplies [1, 2]
Total Fe ions are generally found to be concentrated within the finest fractions, and multiple researchers have argued the sediment Fe levels are significantly correlated with the grain size [17, 18]
The result showed that the algae and shellfish culture impose opposite effects on sediment Fe levels
Summary
Marine culture activities have seen an increase during the last several decades due to the increasing demands for aquaculture products and the need for seafood supplies [1, 2]. Sediment grain size is one of the most basic but important parameters in determining Fe contents. Sediment grain size plays the most fundamental role in determining Fe levels. Sishili Bay is one of the important fishery base and culture area in China It has a culture history of over 70 years. It is famous for scallop culture, accounting for more than 70% of the production in Shandong province In this regard, two cores (in culture area and non-culture area) in Sishili Bay were sampled. Study area and culture activities The studied area, Sishili Bay, is in Yantai City in the northeastern Shandong province, China. Sishili Bay has experienced a long history of cultivation, and is still the most important culture area in the north of China. The grains were divided into four groups: clay (< 4 μm), fine silt (4–16 μm), coarse silt (16–64 μm) and sand (> 64 μm)
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