Lund University, Dept. of Biology, Aquatic Ecology, Sölvegatan 37, 223 62 Lund, Sweden.
Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals, Facultat de Biologia, Universitat de Barcelona, 08028 Barcelona, Spain.
Harmful Algae. 2019 Jun;86:74-83. doi: 10.1016/j.hal.2019.05.005. Epub 2019 May 30.
Nodularia spumigena is a toxic cyanobacteria that blooms in the Baltic Sea every year. In the brackish water of the Baltic Sea, its toxin, nodularin, mainly affects the biota in the surface water due to the natural buoyancy of this species. However, the fate of the toxin is unknown, once the cyanobacteria bloom enters the more saline waters of the Kattegat. In order to investigate this knowledge gap, a bloom of N. spumigena was followed during its passage, carried by surface currents, from the Baltic Sea into the Kattegat area, through the Öresund strait. N. spumigena cells showed an increased cell concentration through the water column during the passage of the bloom (up to 130 10 cells ml), and cells (4.2 10 cells ml) could be found down to 20 m depth, below a pycnocline. Sedimentation trap samples from below the pycnocline (10-12 m depth) also showed an increased sedimentation of N. spumigena filaments during the passage of the bloom. The toxin nodularin was detected both in water samples (0.3-6.0 μg l), samples of sedimenting material (a toxin accumulation rate of 20 μg m day), zooplankton (up to 0.1 ng ind. in copepods), blue mussels (70-230 μg kg DW), pelagic and benthic fish (herring (1.0-3.4 μg kg DW in herring muscle or liver) and flounder (1.3-6.2 μg kg DW in muscle, and 11.7-26.3 μg kg DW in liver). A laboratory experiment showed that N. spumigena filaments developed a decreased buoyancy at increased salinities and that they were even sinking with a rate of up to 1,7 m day at the highest salinity (32 PSU). This has implications for the fate of brackish water cyanobacterial blooms, when these reach more saline waters. It can be speculated that a significant part of the blooms content of nodularin will reach benthic organisms in this situation, compared to blooms decaying in brackish water, where most of the bloom is considered to be decomposed in the surface waters.
节旋藻是一种有毒的蓝藻，每年都会在波罗的海大量繁殖。在波罗的海的半咸水中，由于该物种的自然浮力，其毒素节球藻毒素主要影响地表水生物群。然而，一旦蓝藻水华进入卡特加特海域的盐度更高的水域，毒素的命运就不得而知了。为了研究这方面的知识空白，我们对一个节旋藻水华进行了跟踪研究，该水华通过表层流从波罗的海携带到卡特加特地区，穿过厄勒海峡。在水华通过期间，节旋藻细胞在水柱中表现出浓度增加（最高可达 130×10 个细胞 ml），并且可以在 20 m 以下的深度（在密度跃层下方）发现细胞（4.2×10 个细胞 ml）。密度跃层下方（10-12 m 深度）的沉降捕获器样本也显示，在水华通过期间，节旋藻丝的沉降量增加。在水样（0.3-6.0μg l）、沉降物质样本（毒素积累率为 20μg m day）、浮游动物（桡足类动物中高达 0.1ng ind）、贻贝（70-230μg kg DW）、远洋和底栖鱼类（鲱鱼（肌肉或肝脏中 1.0-3.4μg kg DW）和比目鱼（肌肉中 1.3-6.2μg kg DW，肝脏中 11.7-26.3μg kg DW）中均检测到了毒素节球藻毒素。一项实验室实验表明，节旋藻丝在盐度增加时浮力降低，在最高盐度（32 PSU）下甚至以高达 1.7 m day 的速度下沉。这对当这些半咸水蓝藻水华进入盐度更高的水域时的命运产生了影响。可以推测，与在半咸水中腐烂的水华相比，在这种情况下，大量的水华节球藻毒素将到达底栖生物，因为大部分水华被认为是在地表水分解的。
