REGION: Venezuela
NAME OF THE ASSESSMENT: Heavy metals in the clam Tivela mactroides Born, 1778
(Bivalvia: Venezuela) from coastal localities with different degrees of contamination in
Venezuela.
1 What organization carried out the assessment?
Escuela de Ciencias, Universidad de Oriente, Venezuela y el Instituto Oceanográfico de
Venezuela.
2 Was the assessment a result of an initiative by the body carrying it out? If not,
what body took the initiative that resulted in the assessment?
The assessment was a result of Consejo de Investigación de la Universidad de Oriente y
el Programa de Becas del FONACIT, Venezuela
ORIENTATION
3 What is the context and purpose of the assessment?
A tropical species that may be used as an indicator of contamination is the clam Tivela
mactroides. This bivalve is widely distributed on high-energy beaches in the Caribbean
and can adapt to wide ranges of temperature and salinity; it is easy to collect and always
available owing to its continuous reproduction.
4 Were there explicit objectives for the assessment? If so, what are they?
Yes, the objective is evaluate the concentrations of heavy metals in tissues and shells of
juveniles, medium-size organisms with maturing gonads and adults of Tivela mactroides
from three different locations on the coast of Venezuela.
5 What is the relation of the assessment to the cycle of determining the problems,
adopting measures and evaluating progress?
Their results show that Tivela mactroides is a good biological indicator of the presence of
heavy metals in the littoral waters they inhabit.
COVERAGE AND SOURCES
6 What area does the assessment cover?
Venezuela
7 What were the reasons for selecting the area covered?
Because this bivalve Tivela mactroides is widely distributed on high-energy beaches in the
Caribbean and can adapt to wide ranges of temperatures and salinity; it is easy to collect
and always available owing to its continuous reproduction.
8 What period of time does the assessment cover?
One year
9 How often will assessments of this kind be produced?
Only in mid-July 1999 with three replicas
10 What aspects of the marine ecosystem are covered by the assessment?
Diversity of the clam Tivela mactroides
11 What aspects of human activities and pressures that impact on the marine
environment are covered by the assessment?
Heavy metals levels in the different populations of Tivela mactroides were mainly
influenced by anthropogenic contributions in each zone.
12 On what information is the assessment based?
This information is based in the reported in a previous analysis by Acosta et al., 2002.
13 Where environmental, economic or social data were used, what arrangements
were made for subsequent access to this data by the public or by experts?
Heavy metal concentrations were related to shell size, with significant differences among
populations and shell sizes
14 Where environmental, economic or social data were used, are metadata available
on these data series?
Yes
PROCESS
15 How did the assessment control is the quality of the data used in it?
They selected three populations of Tivela mactroides from high energy beaches with
different levels of contamination. And they collected samples of clams with three replicas
in each location. The levels of heavy metals (manganese, iron, zinc, cadmium, copper,
chromium and lead) in tissues and shells were determined by atomic absorption with a
Perkin Elmer spectrophotometer with an air-acetylene flame determine heavy metals. The
accuracy of our analytical procedures and for every 10 samples, they analyzed tissue
reference standards NIST Oyster Tissue 1566a. The standard deviation values were very
low and similar.
16 Were models of aspects of the marine environment developed and used in the
assessment?
To determine differences among heavy metal levels in tissues and shells of each
population, they applied a two-way analysis of variance, establishing organism size and
origin (population) as factors. In case where significant differences existed (P ˂ 0.05), they
applied Scheffé´s a posteriori test.
17 Did the assessment use any form of indicators?
Yes, the bivalve Tivela mactroides is biological indicator.
18 If the assessment was based (wholly or partly) on traditional knowledge, what
practices were used to control its quality?
They selected three populations of Tivela mactroides from high energy beaches with
different levels of contamination. And they collected samples of clams with three replicas
in each location. The levels of heavy metals (manganese, iron, zinc, cadmium, copper,
chromium and lead) in tissues and shells were determined by atomic absorption with a
Perkin Elmer spectrophotometer with an air-acetylene flame determine heavy metals. The
accuracy of our analytical procedures and for every 10 samples, they analyzed tissue
reference standards NIST Oyster Tissue 1566a. The standard deviation values were very
low and similar.
19 If the assessment was based (wholly or partly) on expert opinion, what practices
were used to control its quality?
No
20 Was any particular conceptual framework used to organize the assessment?
No
21 How were decisions made on which scientific specialisms should be involved,
and how these scientific specialisms should be brought in?
Biology, natural resources
22 How was interaction organized during the assessment process between
scientific, economic and social disciplines and policy makers?
(-)
23 How were non-official stakeholders enabled to participate in the assessment?
(-)
24 Did differences of opinion arise over the conclusions of the assessment? If so,
how were these resolved?
No
25 Was there a peer review of the assessment during the assessment process,
and/or before the final text was published?
Yes, this assessment was made by anonymous reviewers.
26 Were any specific arrangements made to link the assessment with other
contemporary international or national processes?
No
27 Were specific efforts made to strengthen institutional, scientific or technical
capacity for the assessment?
Yes, existed efforts made to strengthen scientific capacity for the assessment.
COMMUNICATIONS
28 In what form was the output of the assessment presented?
The assessment was presented in scientific article
29 In which languages is the assessment available?
The assessment is available in English and Spanish
30 How were the results of the assessment made public?
The results of the assessment was presented in scientific article
CONTENT ON FUTURE ACTIONS
31 Did the assessment rank the severity of problems or otherwise identify priorities
for future action?
Yes
32 Did the assessment evaluate options for future policy, and their likely outcomes?
(-)
33 Did the assessment indicate gaps in the information needed for it?
Yes
34 Did the assessment indicate gaps in the scientific understanding of the relevant
processes that need to be addressed in order to improve the assessment?
Yes
REVIEW
35 Was there a review of the assessment process in order to draw lessons for future
assessments?
This suggests that Tivela mactroides may be used as a good indicator of the presence of
heavy metals on the coast that they inhabit
EXPERT EVALUATION
36 Is the published assessment easy to understand and accessible ton on-specialist
readers?
May be no, because in the assessment used a scientific language
37 To what extent does the assessment give confidence that it provides sound
conclusions that apply to the whole of the area covered?
Tivela mactroides may be used as a good indicator of the presence of heavy metals on the
coast that they inhabit in Venezuela.
38 Does the assessment appear to have been timely in relation to policy
development and the adoption of measures?
Yes
39 Are there any particular strengths or weaknesses in the assessment that are
relevant to the Assessment of Assessments?
The assessment is strengths
40 Does the assessment appear to have been influential in policy making and the
adoption of measures?
(-)