Abstract

Mangrove forests of Biscayne Bay in southeast Florida, USA can sequester pollutants from freshwater inputs. This “filtering” of water minimizes point source discharges through canals, but mangroves may also play an important role in the cycling of plastic pollution that reaches the Bay. The objectives of this study are to determine: 1) The composition of debris in the Bay’s mangroves and 2) How the structure of mangrove forests affects debris distribution. Debris was hypothesized to be more abundant further into the forest due to trapping by vegetation, and mesoplastics (5 mm – 2.5 cm) would be positively correlated to macroplastics (> 2.5 cm) due to fragmentation. Nine transects were surveyed and debris was recorded by size and potential origin. 94.5% of all debris was plastic of which 57.8% were fragments. Negative binomial generalized linear regression was used to relate total plastic and mesoplastic densities to distance from shoreline, elevation, basal area, prop root and pneumatophore cover, and mangrove seedling abundance. Plastic increased with distance from shore and basal area, although the latter was just above the p-value cut-off of 0.05 for mesoplastic (p-value = 0.0513), and was weakly negatively related to prop root coverage. Total plastic was weakly negatively related to red mangrove seedlings and pneumatophore coverage, although these relationships were less clear. Mesoplastic and macroplastic were positively correlated (p-value < 0.05). Selected mangrove forests of Biscayne Bay appear to be sinks for plastic debris, where it accumulates in the interior forest from which it is unlikely to escape.

中文翻译：

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美国佛罗里达州比斯坎湾的红树林可以作为塑料碎片的汇

摘要

美国佛罗里达州东南部比斯坎湾的红树林可以隔离淡水输入中的污染物。这种水的“过滤”最大限度地减少了通过运河的点源排放，但红树林也可能在到达海湾的塑料污染循环中发挥重要作用。本研究的目的是确定：1​​) 海湾红树林中碎片的组成；2) 红树林的结构如何影响碎片分布。据推测，由于植被的截留，碎片在森林深处会更加丰富，并且由于碎片化，中质塑料（5 毫米 - 2.5 厘米）将与大塑料（> 2.5 厘米）呈正相关。对九个横断面进行了调查，并按大小和潜在来源记录了碎片。所有碎片中 94.5% 是塑料，其中 57.8% 是碎片。使用负二项式广义线性回归将总塑性和中塑性密度与距海岸线的距离、海拔、断面积、支柱根和气根覆盖以及红树林幼苗丰度联系起来。塑料随着距海岸和基底面积的距离增加而增加，尽管后者略高于中塑性的p值截止值 0.05（p值 = 0.0513），并且与支柱根覆盖率呈弱负相关。塑料总量与红树幼苗和气团覆盖率呈弱负相关，尽管这些关系不太明确。中塑性和大塑性呈正相关（p值 < 0.05）。比斯坎湾选定的红树林似乎是塑料碎片的汇地，塑料碎片堆积在内部森林中，不太可能逃脱。