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Food web metrics

Results calculated for the EBS food web in the cold and warm regimes in this study shows relatively small differences. All the food web metrics were recorded higher in the cold food web  than in the warm food web, and the calculated dissimilarity in species composition between the two food webs was 96 % (Table 1) . The average  generality represents the mean generalities of the individual predators and average vulnerability represents the mean vulnerabilities of individuals preys.

 

Figure 3: Alluvial diagram showing 7 and 6 groups identified in the cold and warm food webs respectively in the EBS. The floating flows observed in groups 5,2,1 and 0 indicate species that changed groups between the cold and the warm regime while the straight flows between the cold and the warm regime shows species that maintained in the same groups.

Functional groups result

The total 100 species (the 13 predators with respective prey species) were grouped into 7 groups in the cold regime and 6 groups in the warm regime (Figure 3). A total of 32 species out of the 100 total species changed from a particular group in cold regime to a new group in the warm regime, while 71 species maintained the same group across the two temperature regime. Of the 32 species that changed groups 6 were predators and 26 were prey species, which indicates that about 50% of the predator species changed groups.

 

Figure 4: The alluvial diagram showing the four fish guilds exhibit relatively changes between the cold and warm regimes. The total turnover of roundfish guild is very small compared to the other guilds as can been seen between group 5 in the cold years to group 1 in the warm year.

The results also shows how species from different ecological guilds changed groups between the cold and warm regimes as highlighted in Figure 4. It indicates the turnover of the fish guilds between the two temperature regimes for groups 5, 2, 1, 0. The calculated turnover of the fish guilds was 14 % and 83 % for roundfish and flatfish respectively, 23 % and 22% for pelagic and benthic respectively.

Figure 5: The bar chart showing the phyla composition for each functional group in the cold and warm years, phylum Echinodermata was present only in group 2 during the cold years while in the warm years it was recorded in groups 1 and 2. Furthermore, the bar chart also shows variation in diversity within the phyla between the two periods of which in warm years most phyla recorded lower or reduced diversity.

The taxomonic analysis shows that the different groups both in the cold and warm years had high phyla diversity as can be seen in Figure 5 .  Group 0 to 2 were more diverse than group 3 to 6 in both periods. However, there was variaton in the phyla composition in groups 0 and 1 between the two periods with higher numbers of phyla in the warm years. for instance phylum Cnidira was present in group 0 in the cold year but absent in group 0 in the warm years and vice versa for phylum Annelida. There was  also variation in some of phylum diverse  in the different groups between the two period good example is Arthtopoda was more diverse in group 0 and 1 in the warm years than in the cold years.


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Last updated: 10/27/19