Biogeochemical implications for phosphorus cycling in sandy and muddy rhizosphere sediments of Zostera marina meadows (Denmark)
Biogeochemical implications for phosphorus cycling in sandy and muddy rhizosphere sediments of Zostera marina meadows (Denmark)
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大叶藻滨海草甸沙质和泥质根际沉积物中磷循环的生物地球化学意义（丹麦）
DOI：
10.3354/meps320141
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发表时间：
2006
影响因子：
2.5
通讯作者：
F. Andersen
中科院分区：
文献类型：
--
作者：
M. Holmer;C. Carta;F. Andersen
迄今为止，很少有研究探讨沉积物地球化学条件对沉积物磷库和桑迪质（低磷）和泥质（高磷）硅质海草沉积物中磷有效性差异的影响。为了确定海草活动对沉积物磷的季节变化的作用，我们调查了丹麦峡湾海草Zostera marina沉积物中的固相磷库。在Z。通过连续提取，将生长季沉积物分为3个组分（一次分为5个）化学定义的基团：松散吸附的无机磷，与氧化态金属结合的无机磷磷主要以铁结合态磷为主，吸附在粘土矿物、铝和腐殖酸上的磷、钙结合态磷和难降解有机磷等。而在桑迪沉积物中该池较小（80%）。淤泥样地Fe结合态P的季节变化表现为夏末较低，除7月生物量最大期外，在植被覆盖的土壤中Fe结合态P含量始终较低，而在根际土壤中Fe结合态P含量较高。在桑迪场地，沉积磷库的季节变化较小，无植被和有植被的场地差异不大，表明植被对沉积磷库的影响有限。然而，植被的存在增加了两种类型站点水柱中P的有效性，因为与无植被站点在大部分采样期间的吸收相比，在植被站点，P通过沉积物-水界面释放，尽管通量很低，只能解释沉积物P库季节变化的一小部分（<10%）。对海草生物量中P掺入量的估计表明，沉积物中P库的季节变化足以支持对P的需求。我们假设，海草组织中较高的磷含量和泥泞地点较大的生物量是由于该地点氧化还原敏感的铁结合磷库和有机磷库中的高磷可用性，而磷可能是生长的限制因素在桑迪地点，由于钙部分的结合，磷的流动性较低。
To date, few studies have investigated the implications of sediment biogeochemical con- ditions on differences in sediment phosphorus (P) pools and P availability in sandy (low-P) and muddy (high-P) siliclastic seagrass sediments. To determine the role of seagrass activity on seasonal changes in sedimentary P, we investigated the solid-phase P pools in seagrass Zostera marina sedi- ments in a Danish fjord. During the Z. marina growth season sediments were fractionated by sequen- tial extractions into 3 (and once into 5) chemically defined groups: loosely adsorbed inorganic P, inor- ganic P bound to oxidized metals (primarily Fe-bound), P adsorbed to clay minerals, Al and humic acids, Ca-bound P, and refractory organic P. Fe-bound P accounted for about 30% of total P in the muddy sediments, whereas this pool was small in the sandy sediment ( 80%). The Fe-bound P at the muddy site showed seasonal variations with lower pools during late summer, and it was always lower in the vegetated sediment, except dur- ing maximum biomass in July, where Fe-bound P was higher in the deep rhizosphere sediments. The seasonal variation was less at the sandy site, and there was little difference between unvegetated and vegetated sites, suggesting that the vegetation had a limited effect on the sedimentary P pools. How- ever, the presence of vegetation increased the availability of P in the water column at both types of site, as P was released across the sediment-water interface at the vegetated sites compared with an uptake during most of the sampling period at the unvegetated sites, although the fluxes were low and could only account for a minor fraction (<10%) of the seasonal changes in the sedimentary P pools. Estimates of P incorporation in seagrass biomass showed that the seasonal variation in sedimentary P pools were more than sufficient to support the P demand. We hypothesize that the higher P contents in seagrass tissues and the larger biomass at the muddy site are due to high P availability from the redox-sensitive Fe-bound and organic P pools at this site, whereas P may be a limiting factor for growth at the sandy site, where the mobility of P is lower due to binding in the Ca fraction.