陳威 王欣宇 呂寶強(qiáng)
摘要? 紅樹(shù)林生態(tài)系統(tǒng)是沿海生態(tài)系統(tǒng)中獨(dú)特且重要的環(huán)境組成部分。然而,微塑料作為新型環(huán)境污染物通過(guò)不同方式進(jìn)入紅樹(shù)林系統(tǒng)中,已經(jīng)成為紅樹(shù)林面臨的一項(xiàng)嚴(yán)重挑戰(zhàn)。分析了微塑料對(duì)紅樹(shù)林生態(tài)系統(tǒng)的影響,總結(jié)了紅樹(shù)林生態(tài)系統(tǒng)中微塑料分布特征、微塑料對(duì)紅樹(shù)林生態(tài)系統(tǒng)的影響、紅樹(shù)林生態(tài)系統(tǒng)中微塑料分布影響因素、微塑料在紅樹(shù)林生態(tài)系統(tǒng)中的歸宿,最后對(duì)紅樹(shù)林生態(tài)系統(tǒng)中微塑料的研究方向進(jìn)行了展望。提出確立微塑料監(jiān)測(cè)方法和檢測(cè)標(biāo)準(zhǔn)、評(píng)估紅樹(shù)林中微塑料生態(tài)風(fēng)險(xiǎn)、建立微塑料污染治理和管理措施、微塑料模型預(yù)測(cè)、探索修復(fù)與去除策略和研究微塑料與海洋生態(tài)系統(tǒng)碳循環(huán)的相互作用6個(gè)研究,可為未來(lái)紅樹(shù)林微塑料領(lǐng)域研究重點(diǎn)和污染控制提供借鑒。
關(guān)鍵詞? 紅樹(shù)林;微塑料;影響;碳匯
中圖分類(lèi)號(hào)? S718.55?? 文獻(xiàn)標(biāo)識(shí)碼? A? ?文章編號(hào)? 0517-6611(2024)07-0005-05
doi: 10.3969/j.issn.0517-6611.2024.07.002
Research Progress on the Effects of Microplastics on Mangrove Ecosystems
CHEN Wei1, WANG Xinyu2,3?,L??Baoqiang3
(1.Bureau of Natural Resources and Planning of Pingyang,Pingyang,Zhejiang 325088;2.State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin,Heilongjiang 150090;3.Wenzhou University,Wenzhou,Zhejiang 325035)
Abstract? The mangrove ecosystem is a unique and important component of coastal ecosystems.However, microplastics, as a new type of environmental pollutant, enter the mangrove system through various pathways and have become a serious challenge for mangroves.This article analyzes the impact of microplastics on the mangrove ecosystem, including the distribution characteristics of microplastics in the mangrove ecosystem, the effects of microplastics on the mangrove ecosystem, the influencing factors of microplastic distribution in the mangrove ecosystem, and the fate of microplastics in the mangrove ecosystem.Finally, the research directions for microplastics in the mangrove ecosystem are discussed.Six studies were proposed to establish microplastic monitoring methods and detection standards, evaluate the ecological risks of microplastics in mangroves, establish measures for microplastic pollution control and management, predict microplastic models, explore remediation and removal strategies, and study the interaction between microplastics and carbon cycling in marine ecosystems.This study provides references for future research priorities and pollution control in the field of microplastics in mangroves.
Key words? Mangrove;Microplastics;Effects;Carbon sink
紅樹(shù)林主要生長(zhǎng)在亞熱帶和熱帶海岸的潮間帶,被廣泛認(rèn)為是陸地和海洋之間污染物的重要緩沖區(qū)[1-2]。是碳封存、食物和水供應(yīng)、海岸保護(hù)和海洋生物棲息地、環(huán)境凈化和氣候調(diào)節(jié)等重要生態(tài)服務(wù)的主要提供者[3]。由于過(guò)度開(kāi)發(fā),紅樹(shù)林棲息地轉(zhuǎn)變?yōu)檗r(nóng)業(yè)、定居點(diǎn)和工業(yè)用途,紅樹(shù)林面臨著不同程度的威脅[4]。微塑料(microplastics,MP)作為一種新興的、鮮為人知的污染物,引起了世界各地研究人員的關(guān)注[5]。這種污染很普遍,而且可能在未來(lái)有增無(wú)減[6]。自1950年代以來(lái),中國(guó)紅樹(shù)林中的微塑料豐度呈指數(shù)級(jí)增長(zhǎng),預(yù)計(jì)2030年微塑料存量將增加2.38~9.54倍[7]。微塑料通過(guò)陸地或海源來(lái)源匯集到紅樹(shù)林地區(qū)[1],其攜帶的用來(lái)改善性能和耐用性的各種添加劑可能被釋放出來(lái),對(duì)紅樹(shù)林系統(tǒng)產(chǎn)生毒性[8]。而微塑料吸收的有機(jī)物污染物產(chǎn)生的危害更大[9]。紅樹(shù)林中微塑料還能富集抗生素抗性基因和潛在的致病菌[10]。紅樹(shù)林可能是細(xì)菌抗生素耐藥性和多重耐藥性出現(xiàn)和傳播的潛在風(fēng)險(xiǎn)之一,而微塑料生物膜可能是細(xì)菌抗生素耐藥性的促進(jìn)者[11]。微塑料的存在改變了沉積物微生物群落結(jié)構(gòu)和氮循環(huán)過(guò)程[12]。在全球塑料產(chǎn)量和塑料污染劇增的背景下,關(guān)于微塑料對(duì)紅樹(shù)林生態(tài)系統(tǒng)影響研究也迅速增加,然而微塑料對(duì)紅樹(shù)林生態(tài)系統(tǒng)影響仍然很有限,對(duì)于該領(lǐng)域研究的現(xiàn)狀、熱點(diǎn)等問(wèn)題需要進(jìn)一步探索。
該研究通過(guò)web of science檢索2019—2023年微塑料污染對(duì)紅樹(shù)林生態(tài)系統(tǒng)影響的相關(guān)文章,總結(jié)了目前微塑料對(duì)紅樹(shù)林系統(tǒng)的研究動(dòng)態(tài)、熱點(diǎn)和發(fā)展趨勢(shì)等,進(jìn)而為微塑料對(duì)紅樹(shù)林生態(tài)系統(tǒng)的影響及其應(yīng)對(duì)策略等研究提供參考。
1 紅樹(shù)林生態(tài)系統(tǒng)中微塑料的分布特征
紅樹(shù)林可作為海洋垃圾的陷阱[13],對(duì)微塑料具有生態(tài)攔截作用[14]。大多數(shù)研究關(guān)注紅樹(shù)林中微塑料的分布特征。研究紅樹(shù)林中微塑料的分布特征可以指導(dǎo)采取相應(yīng)的控制污染措施。研究表明,微塑料在紅樹(shù)林中分布特征復(fù)雜多樣,可在紅樹(shù)林系統(tǒng)的各個(gè)組成部分中被發(fā)現(xiàn),包括水體、沉積物和生物體中。
1.1 水體中
紅樹(shù)林水體中的微塑料含量可能來(lái)自附近陸地和海洋。微塑料顆??梢噪S著河流流入紅樹(shù)林水體,也可以通過(guò)海洋漂流或潮汐運(yùn)動(dòng)進(jìn)入紅樹(shù)林水域。廈門(mén)西溪紅樹(shù)林地表水中含有微塑料 豐度為620 ~ 13 100 個(gè)/m3[14]。牙買(mǎi)加金斯敦港地表水中微塑料濃度范圍為 0~5.73個(gè)/m3, 這對(duì)在該地區(qū)產(chǎn)卵的海洋生物具有潛在威脅,也威脅現(xiàn)有紅樹(shù)林生態(tài)系統(tǒng)的壽命[15]。孫德?tīng)柋舅梗⊿undarbans)是世界上最大的紅樹(shù)林,其水體中微塑料豐度2.66×103 個(gè)/L[16]。水體中的微塑料可能對(duì)紅樹(shù)林中的水生生物產(chǎn)生直接影響。
1.2 沉積物中
微塑料在紅樹(shù)林的沉積物中廣泛存在。它們可以通過(guò)水流、風(fēng)力和潮汐運(yùn)動(dòng)等方式從陸地或海洋中輸入紅樹(shù)林的沉積物中。微塑料顆粒大小不一,從納米級(jí)到毫米級(jí)都可能存在。它們可能集中在沉積物表面或深入沉積物內(nèi)部。我國(guó)華南沿海紅樹(shù)林沉積物(漲潮線(xiàn))中微塑料豐度為47~35 000個(gè)/kg,時(shí)空分布與風(fēng)向、河流徑流、旅游和漁業(yè)活動(dòng)有關(guān)[17]。人工紅樹(shù)林中MP豐度范圍在(67±21)~(203±25)個(gè)/kg[18]。伊朗的紅樹(shù)林沉降物中共鑒定出2 657種不同大小、顏色、形狀的塑料顆粒,主要為聚苯乙烯、聚丙烯和聚對(duì)苯二甲酸乙二醇酯[19],這也引發(fā)了人們對(duì)紅樹(shù)林微塑料污染的擔(dān)憂(yōu)。另一研究結(jié)果顯示,印度尼西亞Muara Angke野生動(dòng)物保護(hù)區(qū)紅樹(shù)林沉積物樣本中都含有微塑料顆粒[20]。雷州半島紅樹(shù)林中沉積物中微塑料豐度為6.40~255.57個(gè)/kg[21]。
1.3 生物體中
微塑料也可以被紅樹(shù)林植物吸收或附著在其表面。通過(guò)根系吸收,微塑料可能進(jìn)入紅樹(shù)林植物的組織中。此外,微塑料顆粒也可以黏附在植物的葉片、枝干和樹(shù)皮等表面[4,22]。此外,一些動(dòng)物也可能因?yàn)樵诩t樹(shù)林中尋找食物時(shí)與微塑料接觸而受到影響[23]。紅樹(shù)林生態(tài)系統(tǒng)是Periophthalmus waltoni最重要的棲息地之一,伊朗南部紅樹(shù)林中Periophthalmus waltoni魚(yú)體內(nèi)分離出15種微塑料[19]。北部灣紅樹(shù)林中底棲生物Ellobium chinense中微塑料的含量為(95.6±5.0)個(gè)/kg[24]。孟加拉國(guó)孫德?tīng)柋舅辜t樹(shù)林中20種魚(yú)類(lèi)和貝類(lèi)的肌肉和胃腸道中均發(fā)現(xiàn)了微塑料[25],其中底棲和底棲物種受到的污染更嚴(yán)重。我國(guó)華南最大的紅樹(shù)林湛江紅樹(shù)林濕地中,32種魚(yú)類(lèi)中有30種存在微塑料,這項(xiàng)研究表明微塑料在紅樹(shù)林魚(yú)類(lèi)中的廣泛存在[26]。
2 微塑料對(duì)紅樹(shù)林生態(tài)系統(tǒng)的影響
微塑料對(duì)紅樹(shù)林生態(tài)系統(tǒng)的影響是一個(gè)復(fù)雜且多方面的問(wèn)題。了解和評(píng)估微塑料對(duì)紅樹(shù)林的影響對(duì)于保護(hù)紅樹(shù)林生態(tài)系統(tǒng)的健康和可持續(xù)發(fā)展至關(guān)重要,可以為制定相應(yīng)的管理和保護(hù)策略提供科學(xué)依據(jù),有助于減少微塑料對(duì)紅樹(shù)林生物多樣性、生態(tài)功能和生態(tài)系統(tǒng)穩(wěn)定性的潛在影響。
2.1 對(duì)紅樹(shù)林生長(zhǎng)的影響
微塑料對(duì)紅樹(shù)林生態(tài)系統(tǒng)的影響包括直接影響和潛在影響,例如土壤質(zhì)量的下降、水體污染和植物生長(zhǎng)受限等。微塑料直接影響為植物部位積累并阻礙養(yǎng)分吸收[22]。微塑料的存在會(huì)改變土壤的物理和化學(xué)性質(zhì),可能會(huì)影響植物群落組成。微塑料能夠?qū)е录t樹(shù)林海水和沉積物的物理化學(xué)組成發(fā)生變化,破壞土壤的結(jié)構(gòu)[27]。微塑料還能抑制植物的光合作用從而影響紅樹(shù)林植物生長(zhǎng)[28]。紅樹(shù)林在全球范圍內(nèi)被大量塑料垃圾污染,微塑料所形成的塑料際(plasticsphere)是新的生態(tài)位,微塑料與根際微生物之間的相互作用可能會(huì)影響紅樹(shù)林植物的生長(zhǎng)和健康[29]。此外,紅樹(shù)林中微塑料了攜帶Cr、Zn、Pb、Cd等重金屬,成為重金屬的載體[30]。微塑料的釋放和降解還可能導(dǎo)致水體污染,危及紅樹(shù)林生長(zhǎng)。
2.2 對(duì)生物多樣性的影響
微塑料對(duì)生物群落豐度和紅樹(shù)林生產(chǎn)有負(fù)面影響[31]。它們可以被紅樹(shù)林動(dòng)植物誤食,導(dǎo)致消化道堵塞、毒素釋放和能量攝取減少。微塑料的存在還可能改變物種的行為和生態(tài)位,對(duì)紅樹(shù)林中的生態(tài)平衡造成影響。紅樹(shù)林中草食性蝸牛與葉片總的中塑料和微塑料豐度和具有相同的特征的比例呈顯著正相關(guān),并抑制蝸牛替體內(nèi)細(xì)胞轉(zhuǎn)導(dǎo)[32]。紅樹(shù)林的微塑料威脅著魚(yú)類(lèi)和軟體動(dòng)物的生存[33]。孫德?tīng)柋舅乖谒?、沉積物和魚(yú)體中受到微塑料的污染,其數(shù)量比任何其他研究描述的都要多,對(duì)生態(tài)和野生動(dòng)物構(gòu)成了更大的風(fēng)險(xiǎn)[16]。對(duì)湛江紅樹(shù)林沉積物微生物群落結(jié)構(gòu)分析發(fā)現(xiàn),微塑料可能會(huì)影響沉積物中微生物的多樣性和豐富度[34]。
2.3 對(duì)碳匯的影響
紅樹(shù)林是重要的碳匯,具有顯著的碳吸收和儲(chǔ)存能力。然而,紅樹(shù)林中微塑料的存在可能對(duì)其作為碳匯的功能產(chǎn)生一定的影響。這是一個(gè)新型的研究領(lǐng)域,目前缺乏全面的了解,微塑料的污染可能對(duì)紅樹(shù)林生態(tài)系統(tǒng)的健康和碳吸收能力產(chǎn)生負(fù)面影響。首先,微塑料的存在可能對(duì)紅樹(shù)林植物的生長(zhǎng)和生理過(guò)程產(chǎn)生負(fù)面影響。微塑料顆粒的積聚可能阻塞植物的氣孔,影響氣體交換和光合作用,從而降低植物的生長(zhǎng)和碳吸收能力。其次,微塑料的存在可能對(duì)紅樹(shù)林土壤的碳循環(huán)產(chǎn)生影響。微塑料顆??梢栽谕寥乐蟹e聚,并影響土壤微生物的活動(dòng)和土壤有機(jī)質(zhì)的分解速率。這可能導(dǎo)致土壤碳的釋放或減少,從而影響紅樹(shù)林作為碳匯的能力。沉積物中微塑料通過(guò)改變碳通量和碳封存影響全球海洋碳匯變化[35]。香港沿海沉積物中微塑料對(duì)不同深度的沉積物碳庫(kù)的貢獻(xiàn)估計(jì)值為0.001%~1.197%,為沿海沉積物的碳儲(chǔ)量做出了隱藏的貢獻(xiàn)[9]。對(duì)于總的沿海藍(lán)碳系統(tǒng)來(lái)說(shuō),微塑料數(shù)量的增加有可能影響有機(jī)碳封存,微塑料的高豐度和毒性增加了沿海藍(lán)碳系統(tǒng)的健康和可持續(xù)發(fā)展[36]。此外,微塑料顆粒在紅樹(shù)林濕地中的沉積可能導(dǎo)致底棲生物受影響。底棲生物是紅樹(shù)林生態(tài)系統(tǒng)中重要的環(huán)節(jié),它們參與有機(jī)質(zhì)的分解和碳循環(huán)過(guò)程。微塑料對(duì)底棲生物的影響可能影響其生態(tài)功能,進(jìn)而影響紅樹(shù)林濕地的碳循環(huán)和碳匯能力。
3 紅樹(shù)林生態(tài)系統(tǒng)中微塑料分布影響因素
3.1 物理因素
紅樹(shù)林環(huán)境具有獨(dú)特的水動(dòng)力學(xué)、潮汐和鹽度等物理特征,這可能對(duì)微塑料的命運(yùn)產(chǎn)生影響。研究這些環(huán)境因素對(duì)微塑料行為和分布的影響,有助于更好地理解微塑料在紅樹(shù)林中的遷移和積累規(guī)律。例如,河流的流速和潮汐的漲落可以影響微塑料在水體中的輸運(yùn)和沉降,從而影響其在紅樹(shù)林中的分布。北部灣的紅樹(shù)林中表層沉積物樣本中微塑料豐度從低潮帶向高潮帶逐漸增加,且豐度與顆粒有機(jī)碳顯著相關(guān)[37-38]。在紅樹(shù)林的不同區(qū)域,漲潮和退潮期間潮汐流速度和微塑料含量之間具有很強(qiáng)的線(xiàn)性關(guān)系,此研究結(jié)果強(qiáng)調(diào)在探索紅樹(shù)林生態(tài)系統(tǒng)中微塑料分布的機(jī)制時(shí),應(yīng)考慮潮汐流速度和潮汐范圍[39]。赤道地區(qū)(新加坡)海岸微塑料分布受季風(fēng)和集水區(qū)特征影響,沉積物的MP和降雨量存在反比關(guān)系[40]。
3.2 生物因素
紅樹(shù)林生物活動(dòng)對(duì)微塑料的分布也可能起到重要作用。動(dòng)物的活動(dòng),例如攝食,可以改變微塑料的沉積和分布方式。此外,生物的生理特征和行為習(xí)性也可能導(dǎo)致微塑料在紅樹(shù)林生物體內(nèi)的富集和轉(zhuǎn)移。紅樹(shù)林生物種類(lèi)繁多,也可作為微塑料的儲(chǔ)存庫(kù)。紅樹(shù)林中定居的海洋生物捕獲微塑料存儲(chǔ)在體內(nèi)[1]。原始紅樹(shù)林調(diào)查中發(fā)現(xiàn)海綿中MPs豐度(1 861~3 456個(gè)/kg),遠(yuǎn)高于沉積物和海水中[41]。紅樹(shù)林中植物在保留微塑料方面發(fā)揮著不可替代的作用,華南保護(hù)區(qū)紅樹(shù)林邊緣的微塑料和纖維總量明顯高于其內(nèi)部和泥灘,而微塑料的豐度和Sonneratia spp.的氣團(tuán)密度之間存在顯著的正相關(guān)性。Sonneratia caseolaris林分的森林內(nèi)部發(fā)現(xiàn)的纖維和 PET 明顯多于S.apetala林分[42]。
3.3 人類(lèi)活動(dòng)
紅樹(shù)林周邊的污染源和人類(lèi)活動(dòng)會(huì)直接或間接地影響微塑料的分布,包括水產(chǎn)養(yǎng)殖、農(nóng)業(yè)和居住生活等[37]。塑料垃圾的排放、塑料制品的使用和塑料生產(chǎn)過(guò)程中的漏損都可能導(dǎo)致微塑料進(jìn)入紅樹(shù)林生態(tài)系統(tǒng)。印度城市紅樹(shù)林土壤、沉積物和水中發(fā)現(xiàn)了微塑料,且聚合物是那些幾乎沒(méi)有被回收的聚合物[43]。此外,旅游、漁業(yè)和沿海開(kāi)發(fā)等人類(lèi)活動(dòng)也可能增加微塑料在紅樹(shù)林中的存在。微塑料豐度與人口密度及國(guó)內(nèi)生產(chǎn)總值呈顯著正相關(guān)[44]。樂(lè)清灣紅樹(shù)林沉積剖面中微塑料豐度隨著深度的增加而降低,受工業(yè)水平提高的直接影響,主要來(lái)源是徑流輸入[45]。雷州半島海岸紅樹(shù)林沉積物中微塑料豐度高的主要原因是人口稠密的城市居民和流動(dòng)游客[21]。越南北部紅樹(shù)林沉積物巖心深度低于70 cm的樣品中為觀察到微塑料,這也反映了人類(lèi)活動(dòng)對(duì)微塑料污染的影響[46]。
綜上所述,紅樹(shù)林中微塑料的分布特征受到多個(gè)因素的綜合影響。理解這些影響因素對(duì)于評(píng)估微塑料在紅樹(shù)林生態(tài)系統(tǒng)中的風(fēng)險(xiǎn)和采取適當(dāng)?shù)墓芾泶胧┲陵P(guān)重要。進(jìn)一步的研究和監(jiān)測(cè)工作有助于深入了解紅樹(shù)林中微塑料的分布規(guī)律和影響機(jī)制。
4 微塑料在紅樹(shù)林生態(tài)系統(tǒng)中的歸宿
4.1 積累
紅樹(shù)林植被積累微塑料[47],紅樹(shù)林沉積物對(duì)微塑料具有捕獲作用[45],根系和樹(shù)干等結(jié)構(gòu)可以捕集和積累微塑料顆粒。紅樹(shù)林的根系網(wǎng)絡(luò)和縱向生長(zhǎng)能力使其成為微塑料的陷阱。這種捕集和積累作用可以減少微塑料進(jìn)入紅樹(shù)林水體和其他生態(tài)系統(tǒng)的可能性,起到一定程度的凈化作用。微塑料顆粒傾向于在紅樹(shù)林水體中沉降,并富集在底泥和植物表面等區(qū)域。紅樹(shù)林的樹(shù)根和樹(shù)干結(jié)構(gòu)可以攔截微塑料顆粒,并促使其在紅樹(shù)林中積累。粵港澳大灣區(qū)紅樹(shù)林微塑料分布調(diào)查中發(fā)現(xiàn)紅樹(shù)林森林邊緣的微塑料豐度高于森林內(nèi)部[48]。已有研究表明,紅樹(shù)林在微塑料從河流到海洋的運(yùn)輸中具有截留作用。紅樹(shù)林對(duì)河流微塑料的截留率旱季為12.86%~5600%,雨季為10.57%~42.00%。密度高、體積大、形狀規(guī)則的微塑料更容易被截獲。此外,生態(tài)指標(biāo)、紅樹(shù)林特性和水動(dòng)力因素的綜合影響共同決定了微塑料的截留率[49]。
4.2 遷移
微塑料顆粒在紅樹(shù)林水體中可以通過(guò)水流、潮汐和海浪等因素發(fā)生遷移和轉(zhuǎn)運(yùn)。了解微塑料在紅樹(shù)林不同媒介中的遷移過(guò)程,有助于揭示其在紅樹(shù)林生態(tài)系統(tǒng)中的分布模式和傳輸途徑。紅樹(shù)林一些生物可能會(huì)誤食紅樹(shù)林中的微塑料顆粒,從而使微塑料進(jìn)入食物鏈并傳遞到更高層級(jí)的生物中。在亞熱帶紅樹(shù)林生態(tài)系統(tǒng)中發(fā)現(xiàn)微塑料豐度隨著營(yíng)養(yǎng)級(jí)的增加而增加,微塑料已被證明在不同的營(yíng)養(yǎng)級(jí)之間轉(zhuǎn)移,在連續(xù)營(yíng)養(yǎng)級(jí)中存在生物放大[50]。水分滲入和土壤動(dòng)物活動(dòng)可引起微塑料向下遷移[51]。微塑料可通過(guò)食物鏈進(jìn)行遷移,微塑料進(jìn)入植物或動(dòng)物體內(nèi),被人攝入,排出體外完成微塑料的遷移過(guò)程[52-53]。
4.3 降解
紅樹(shù)林環(huán)境中的物理、化學(xué)和生物過(guò)程可能促進(jìn)微塑料的降解和轉(zhuǎn)化。例如,風(fēng)化[54]、紫外線(xiàn)[55]、熱處理[56]和微生物[57]的作用可能導(dǎo)致微塑料顆粒的分解和降解,使其逐漸轉(zhuǎn)化為較小的顆?;蚧瘜W(xué)物質(zhì)。紅樹(shù)林中塑料碎片分解成微塑料,微塑料隨后被生物降解,微塑料生物降解受微生物特性和環(huán)境因素的影響,且涉及多種生化反應(yīng)[58]。紅樹(shù)林生態(tài)系統(tǒng)中微生物種類(lèi)繁多,目前已發(fā)現(xiàn)降解PE的細(xì)菌和真菌[59-60]。原位培養(yǎng)試驗(yàn)證明,1個(gè)月培養(yǎng)后9種微塑料基質(zhì)中3種發(fā)生了降解[29]。利用EPS富集到了具有相似群落結(jié)構(gòu)降解聚集體,PS降解菌的有可能為氧化途徑[61]。這些結(jié)果表明紅樹(shù)林根際微生物是微塑料生物降解的理想候選者之一。
4.4 長(zhǎng)期積累和釋放
微塑料在紅樹(shù)林濕地中可能長(zhǎng)期積累,尤其是在沉積物中。這可能導(dǎo)致微塑料的長(zhǎng)期存在和釋放,影響紅樹(shù)林濕地的生態(tài)系統(tǒng)功能和物質(zhì)循環(huán)。有研究發(fā)現(xiàn),在紅海和阿拉伯灣紅樹(shù)林陳年沉積物芯中提取到了微塑料,且<0.5 mm的微塑料在紅樹(shù)林沉積物中占主導(dǎo)地位,自1950年以來(lái)塑料掩埋率呈指數(shù)增長(zhǎng),證實(shí)了紅樹(shù)林沉積物是長(zhǎng)期的匯[62]。對(duì)中國(guó)紅樹(shù)林中微塑料垂直分布調(diào)查發(fā)現(xiàn)最古老的微塑料可追溯到1955年左右[7]。沉積物中微塑料在受到擾動(dòng)后會(huì)隨著海底沉積物再懸浮,從而被釋放到海水中[63]。
需要指出的是,微塑料在紅樹(shù)林中的具體命運(yùn)還存在許多未解之謎,需要進(jìn)一步研究。此外,微塑料的輸入和管理策略也是減少微塑料在紅樹(shù)林中的存在和影響的關(guān)鍵。因此,加強(qiáng)微塑料在紅樹(shù)林中的監(jiān)測(cè)、研究和管理非常重要,有助于保護(hù)紅樹(shù)林生態(tài)系統(tǒng)的健康和可持續(xù)發(fā)展。
5 研究展望
紅樹(shù)林中微塑料研究是一個(gè)新興的領(lǐng)域,盡管已經(jīng)取得了一些進(jìn)展,但仍有許多方面需要進(jìn)一步探索和研究:
(1)微塑料監(jiān)測(cè)方法和檢測(cè)標(biāo)準(zhǔn)的確立。發(fā)展更準(zhǔn)確、高效的微塑料監(jiān)測(cè)方法和技術(shù)及標(biāo)準(zhǔn)是關(guān)鍵。目前,微塑料的檢測(cè)和鑒定仍面臨挑戰(zhàn),沒(méi)有統(tǒng)一的檢測(cè)標(biāo)準(zhǔn)。進(jìn)一步發(fā)展適用于紅樹(shù)林環(huán)境的現(xiàn)場(chǎng)監(jiān)測(cè)工具和技術(shù)及檢測(cè)標(biāo)準(zhǔn),可以更全面地了解微塑料在紅樹(shù)林中的存在和分布。
(2)紅樹(shù)林中微塑料生態(tài)風(fēng)險(xiǎn)評(píng)估。進(jìn)一步開(kāi)展紅樹(shù)林中微塑料的生態(tài)風(fēng)險(xiǎn)評(píng)估是重要的研究方向。這涉及對(duì)微塑料的毒性和累積效應(yīng)進(jìn)行深入研究,以及微塑料對(duì)紅樹(shù)林生物多樣性、生態(tài)功能和生態(tài)系統(tǒng)穩(wěn)定性的潛在影響的評(píng)估,為制定有效的管理和保護(hù)策略提供科學(xué)依據(jù)。
(3)微塑料污染治理和管理措施建立。開(kāi)展紅樹(shù)林微塑料污染治理和管理措施的研究也是關(guān)鍵。包括減少塑料和微塑料源的排放和輸入,發(fā)展可持續(xù)的塑料替代品,以及改善廢棄物管理和回收系統(tǒng)等。此外,開(kāi)展公眾意識(shí)提高活動(dòng),促進(jìn)社會(huì)的塑料減量和可持續(xù)消費(fèi)行為也是必要的。
(4)微塑料模型預(yù)測(cè)。建立數(shù)值模型來(lái)模擬和預(yù)測(cè)紅樹(shù)林中微塑料的遷移、轉(zhuǎn)化和累積過(guò)程。這些模型可以結(jié)合環(huán)境因素、塑料特性和生態(tài)參數(shù)等,提供更準(zhǔn)確的預(yù)測(cè),為管理和決策提供科學(xué)依據(jù)。
(5)修復(fù)與去除策略探索。探索紅樹(shù)林中微塑料的修復(fù)和去除策略。研究紅樹(shù)林生態(tài)系統(tǒng)中的微塑料去除技術(shù)和廢棄物管理方法,以及植物修復(fù)和生態(tài)恢復(fù)措施,為紅樹(shù)林中微塑料的去除提供科學(xué)依據(jù)。
(6)微塑料與海洋生態(tài)系統(tǒng)碳循環(huán)的相互作用。深入了解微塑料與海洋生態(tài)系統(tǒng)中關(guān)鍵生物和生態(tài)過(guò)程之間的相互作用,例如光合作用、呼吸作用和有機(jī)碳沉積等。研究微塑料如何干擾這些過(guò)程,以及對(duì)海洋碳循環(huán)的影響程度,揭示微塑料對(duì)海洋碳匯的潛在影響機(jī)制。
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作者簡(jiǎn)介?? 陳威(1987—),男,浙江溫州人,工程師,碩士,從事海洋生態(tài)保護(hù)研究。
通信作者,高級(jí)工程師,碩士,從事生態(tài)環(huán)境監(jiān)測(cè)與評(píng)價(jià)研究。