Turley Brendan D, Karnauskas Mandy, Campbell Matthew D, Hanisko David S, Kelble Christopher R
Cooperative Institute for Marine and Atmospheric Studies, Rosenstiel School for Marine and Atmospheric Science, University of Miami, 4600 Rickenbacker Causeway, Miami, FL, USA 33149; NOAA Southeast Fisheries Science Center, 75 Virginia Beach Drive, Miami, FL, USA 33149.
NOAA Southeast Fisheries Science Center, 75 Virginia Beach Drive, Miami, FL, USA 33149.
Harmful Algae. 2022 May;114:102223. doi: 10.1016/j.hal.2022.102223. Epub 2022 Mar 24.
Harmful algal blooms (HABs) caused by the dinoflagellate Karenia brevis on the West Florida Shelf have become a nearly annual occurrence causing widespread ecological and economic harm. Effects range from minor respiratory irritation and localized fish kills to large-scale and long-term events causing massive mortalities to marine organisms. Reports of hypoxia on the shelf have been infrequent; however, there have been some indications that some HABs have been associated with localized hypoxia. We examined oceanographic data from 2004 to 2019 across the West Florida Shelf to determine the frequency of hypoxia and to assess its association with known HABs. Hypoxia was present in 5 of the 16 years examined and was always found shoreward of the 50-meter bathymetry line. There were 2 clusters of recurrent hypoxia: midshelf off the Big Bend coast and near the southwest Florida coast. We identified 3 hypoxic events that were characterized by multiple conductivity, temperature, and depth (CTD) casts and occurred concurrently with extreme HABs in 2005, 2014, and 2018. These HAB-hypoxia events occurred when K. brevis blooms initiated in early summer months and persisted into the fall likely driven by increased biological oxygen demand from decaying algal biomass and reduced water column ventilation due to stratification. There were also four years, 2011, 2013, 2015, and 2017, with low dissolved oxygen located near the shelf break that were likely associated with upwelling of deeper Gulf of Mexico water onto the shelf. We had difficulty in assessing the spatiotemporal extent of these events due to limited data availability and potentially unobserved hypoxia due to the inconsistent difference between the bottom of the CTD cast and the seafloor. While we cannot unequivocally explain the association between extreme HABs and hypoxia on the West Florida Shelf, there is sufficient evidence to suggest a causal linkage between them.
由短裸甲藻引起的有害藻华在西佛罗里达陆架几乎每年都会发生，造成广泛的生态和经济损害。其影响范围从轻微的呼吸道刺激和局部鱼类死亡到大规模、长期的事件，导致海洋生物大量死亡。陆架上关于缺氧的报告并不常见；然而，有一些迹象表明，一些有害藻华与局部缺氧有关。我们研究了2004年至2019年西佛罗里达陆架的海洋学数据，以确定缺氧的频率，并评估其与已知有害藻华的关联。在所研究的16年中，有5年存在缺氧情况，且总是在50米等深线向岸一侧发现。有2组反复出现的缺氧区域：大弯海岸外的陆架中部和佛罗里达西南海岸附近。我们确定了3次缺氧事件，其特征是有多次电导率、温度和深度（CTD）测量，并且分别在2005年、2014年和2018年与极端有害藻华同时发生。这些有害藻华 - 缺氧事件发生在短裸甲藻藻华于初夏开始并持续到秋季时，可能是由于腐烂藻类生物量导致生物需氧量增加以及分层导致水柱通风减少所致。另外在2011年、2013年、2015年和2017年，在陆架边缘附近也存在低溶解氧情况，这可能与墨西哥湾较深层水上升到陆架有关。由于数据可用性有限以及CTD测量底部与海底之间存在不一致差异可能导致未观测到的缺氧情况，我们难以评估这些事件的时空范围。虽然我们无法明确解释西佛罗里达陆架上极端有害藻华与缺氧之间的关联，但有足够的证据表明它们之间存在因果联系。
