assemblages close to epibenthic patches are enriched in polychaets

Aricidea nolani, Chaetozone setosa, Heteromastus filiformis,

Scoloplos armiger and oligochaetes

BackgroundBackground

Epibenthic patches (EPs) dominated by barnacles, ascidians Epibenthic patches (EPs) dominated by barnacles, ascidians and red algaeand red algae based based onon shells shells,, small stones small stones and boulders and boulders are the primary source of topographic heterogeneity in soft are the primary source of topographic heterogeneity in soft bottoms of the White Sea near Solovetsky islandsbottoms of the White Sea near Solovetsky islands. . Previous Previous findings show that ffindings show that five of the ten top abundant ive of the ten top abundant macrobenthic taxa (polychaetes macrobenthic taxa (polychaetes Aricidea nolaniAricidea nolani,, Chaetozone Chaetozone setosasetosa, , Heteromastus filiformisHeteromastus filiformis, , Scoloplos armigerScoloplos armiger and and oligochaetes) were associated with the cores sampled close oligochaetes) were associated with the cores sampled close to EPsto EPs compared to the cores 25-25 cm apart of them. compared to the cores 25-25 cm apart of them. Manipulative experiments to reveal an effect of biogenic or Manipulative experiments to reveal an effect of biogenic or non-biogenic obstacles on the surrounding benthic non-biogenic obstacles on the surrounding benthic assemblages have been never previously arranged.assemblages have been never previously arranged.

EFFECT OF HARD STRUCTURES ON THE SURROUNDING EFFECT OF HARD STRUCTURES ON THE SURROUNDING BENTHIC ASSEMBLAGE OF THE SOFT SEDIMENTBENTHIC ASSEMBLAGE OF THE SOFT SEDIMENT

Eugeniy YakovisEugeniy Yakovis**, Anna Artemieva, Marina Varfolomeeva, Natalia Shunatova, Anna Artemieva, Marina Varfolomeeva, Natalia Shunatova*Email: yakovis@rbcmail.ru*Email: yakovis@rbcmail.ru

Invertebrate Zoology Department, St.-Petersburg State University, Universitetskaya nab. 7/9, 199034, St.-Invertebrate Zoology Department, St.-Petersburg State University, Universitetskaya nab. 7/9, 199034, St.-Petersburg, RussiaPetersburg, Russia

The WhiteThe WhiteSeaSea

65° 01.2’35° 39.7’

ExperimentsExperiments

In 2005 and 2006 we In 2005 and 2006 we placed obstacles placed obstacles (concrete bricks, (concrete bricks, (30(30151510 cm)10 cm) on on unstructured sedimentunstructured sediment

toto separate physical separate physical and biogenic distant and biogenic distant effects of epibenthic effects of epibenthic patches (2 runs patches (2 runs 5 5 bricksbricks 2 cores before 2 cores before and after the and after the manipulation).manipulation).

For each species:

Repeated Measures ANOVA

Run 2005-2006 2006-2007

( before) = ( ) - ( ),

w here is a position (1...5 )

for Factors:

(2 leve ls, and )

D eltaN i, i i

i

D e ltaN

N Nb e f o r e / c o n t r o l b e f o r e / t r e a t m e n t

D eltaN i, i i( a fte r) = ( ) - ( ),

(2 leve ls, and )

+

for B ray-C urtis d issim ila rity betw een the pa ired contro l and treatm entsam ples

Factors: (2 leve ls, and ) (2 leve ls, and )

if the d iffe rence betw een pa ired contro l and treatm entchanged significantly afte r a year o f exposure ,w e considered th is as a response to m anipula tion

N Nb e f o r e / c o n t r o l b e f o r e / t r e a t m e n t

Time before after

Repeated Measures ANOVA

Run 2005-2006 2006-2007Time before after

U nivaria te analysis exp la ined

before /trea tm ent

a fte r/trea tm ent

before /contro l

a fte r/contro l

treatm ent - add ing the bricks

exposure - 12 m onths

sam pling

sam pling

1 2 3 4 5pos.

time

55 sq cm55 sq cmcorescores

bricksbricks

No effect on assemblagesNo effect on assemblages

Assemblages were numerically dominated by the tube-building maldanid polychaete Rhodine loveni and oligochaetes. Repeated measures ANOVA and Wilcoxon matched pairs test revealed no significant effect of the manipulation on Bray-Curtis dissimilarity between paired Control and Impact samples. On the nMDS plot Before- and After-Control groups of samples were clearly separated, whereas the After-Treatment group was shifted in relation to the other three, but with a large overlap. ANOSIM R-s showed significant differences between Before- and After-Control groups and in pairs After-Treatment vs Before-Control, After-Control vs Before-Treatment. Closest similarity was between After-Control and After-Treatment groups. There was no effect of manipulation on the difference in biomasses between Control and Treatment samples in any of the four principal feeding guilds as well as on the corresponding difference in the ratio of biomasses of surface and subsurface deposit feeders.

3 of 10 top abundant 3 of 10 top abundant species affectedspecies affected

Scoloplos armiger and Heteromastus filiformis positively responded to the manipulation, i.e. treatments increased their abundance relatively to control samples, whilst Apistobranchus tullbergi demonstrated the significant negative response. Scoloplos armiger and Heteromastus filiformis significantly decreased their density in Control samples (746±76 to 294±29 and 814±83 to 542±45 m-2) and increased them in Treatment ones (407±55 to 881±73 and 497±53 to 746±67 m-2). In the surrounding sediment Heteromastus filiformis significantly increased its density in 2005-2007 (377±53 to 910±205  m-2, 2-tail Student T-test, p<0.001), whereas Scoloplos armiger insignificantly decreased one (565±61 to 432±116 m-2).Against the background of insignificant density increase in 2005-2007 (from 630±61 to 728±172 m-2, Student T-test) A. tullbergi increased its average density in Treatment cores (362±78 to 667±71 m-2) much less than in Control ones (260±40 to 1040±122 m-2).

Stress: 0,28

positively affectedpositively affected::Heteromastus filiformisHeteromastus filiformis, ,

Scoloplos armigerScoloplos armiger

negatively affected:negatively affected:Apistobranchus tullbergiApistobranchus tullbergi

nMDS on Bray-Curtis dissimilarity

before-control, before-treatment,

after-control, after-treatment