Guidetti P, Dulcić J
Laboratory of Zoology and Marine Biology, DiSTeBA, University of Lecce, via prov.le Monteroni, 73100 Lecce, Italy.
Mar Environ Res. 2007 Mar;63(2):168-84. doi: 10.1016/j.marenvres.2006.08.002. Epub 2006 Aug 30.
Previous studies conducted on a local scale emphasised the potential of trophic cascades in Mediterranean rocky reefs (involving predatory fish, sea urchins and macroalgae) in affecting the transition between benthic communities dominated by erected macroalgae and barrens (i.e., bare rock with partial cover of encrusting algae). Distribution patterns of fish predators of sea urchins (Diplodus sargus sargus, Diplodus vulgaris, Coris julis and Thalassoma pavo), sea urchins (Paracentrotus lividus and Arbacia lixula) and barrens, and fish predation rates upon sea urchins, were assessed in shallow (3-6m depth) sublittoral rocky reefs in the northern, central and southern sectors of the eastern Adriatic Sea, i.e., on a large spatial scale of hundreds of kilometres. No dramatic differences were observed in predatory fish density across latitude, except for a lower density of small D. sargus sargus in the northern Adriatic and an increasing density of T. pavo from north to south. P. lividus did not show any significant difference across latitude, whereas A. lixula was more abundant in the southern than in the central Adriatic. Barrens were more extended in the southern than in the central and northern sectors, and were related with sea urchin density. Fish predation upon adult sea urchins did not change on a large scale, whereas it was slightly higher in the southern sector for juveniles when predation rates of both urchins were pooled. Results show that: (1) assemblages of predatory fish and sea urchins, and barren extent change across latitude in the eastern Adriatic Sea, (2) the weak relations between predatory fish density and predation rates on urchins reveal that factors other than top-down control can be important over large scale (with the caveat that the study was conducted in fished areas) and (3) patterns of interaction among strongly interacting taxa could change on large spatial scales and the number of species involved.
以往在局部尺度上进行的研究强调了地中海岩礁中营养级联（涉及掠食性鱼类、海胆和大型藻类）在影响由直立大型藻类主导的底栖生物群落与荒芜区域（即覆盖有结壳藻类的裸岩）之间转变方面的潜力。在亚得里亚海东部北部、中部和南部浅海（深度3 - 6米）的亚潮带岩礁中，即在数百公里的大空间尺度上，评估了海胆（萨氏笛鲷、普通笛鲷、朱红锦鱼和孔雀锦鱼）、海胆（紫球海胆和刺冠海胆）和荒芜区域的鱼类捕食者分布模式，以及鱼类对海胆的捕食率。除了亚得里亚海北部小型萨氏笛鲷密度较低以及孔雀锦鱼从北向南密度增加外，未观察到掠食性鱼类密度在纬度上有显著差异。紫球海胆在纬度上没有显示出任何显著差异，而刺冠海胆在亚得里亚海南部比中部更为丰富。荒芜区域在南部比中部和北部更为广泛，且与海胆密度相关。鱼类对成年海胆的捕食在大尺度上没有变化，而当合并两种海胆的捕食率时，幼体在南部区域的捕食率略高。结果表明：（1）在亚得里亚海东部，掠食性鱼类和海胆的组合以及荒芜区域范围随纬度变化；（2）掠食性鱼类密度与对海胆的捕食率之间的弱关系表明，除了自上而下的控制外，其他因素在大尺度上可能也很重要（需要注意的是该研究是在捕捞区域进行的）；（3）强相互作用类群之间的相互作用模式可能在大空间尺度上发生变化，且涉及的物种数量也会改变。
