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English as a Second Language/Bizarre use of the past perfect

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Dear AGM,

Greetings from Russia, and I hope you had a great Thanksgiving Day.

Please take a look at the following excerpts from published microbiological-research literature:

1. Four major phylogenetic groups, Alpha-, Beta-, and Gammaproteobacteria subgroups and the Cytophaga-Flavobacterium (CF) cluster, were investigated by FISH. Bacterial abundance increased in the control incubation (Fig. 5a), but the community composition was relatively stable throughout the experiment according to FISH (Fig. 5b). At time 0, Betaproteobacteria were more abundant than all other groups, but HAD DECREASED by day 3. The relative abundance of the other three bacterial groups also varied during the experiment, but all four groups were present at each time-point.

In contrast, the glucose-amended treatment was dominated by a few phylogenetic groups after the initial time-point (Fig. 5b). On day 3, Beta- and Gammaproteobacteria together comprised 40% of the DAPI-stained cells. By day 10, Betaproteobacteria were the most abundant group, while the abundance of Gammaproteobacteria HAD DECREASED to less than 5%. By day 25, Betaproteobacteria HAD DECREASED to undetectable levels. Both Alphaproteobacteria and the CF cluster were less than or equal to 10% of prokaryotic abundance throughout the experiment.

2. The toxicity of selenite to bacteria and algae is well known [6,13,27]. In this study, selenite was clearly inhibitory to the growth of the filamentous, polymorphic and unicellular fungi at millimolar concentrations, although some were able to grow at selenite concentrations up to 5 mmol L. It should be made clear, however, that growth measurements were not taken after 14 days incubation. Therefore, it is possible that fungi incubated in the presence of selenite which HAD SHOWN no growth AFTER this time may have exhibited growth after further incubation.

I am sorry for the long quotations, but I just wanted to provide a minimum of context.

My question is, is the use of the past perfect justified in these examples? To me, the things described sound just like a simple succession of events, requiring the simple past – at time 0, the bacteria were abundant; by day 3, their abundance decreased; by day 25, it decreased even further; etc. My guess is that in either example 1 or example 2, we are dealing with some kind of an attempt at summing up the research results with reference to the past, but aren’t those simply cases of tense misuse? What do you think?

Thanks very much for your comments,

Dmitry

Answer
Hi Dmitry,

I had a good Thanksgiving, thank you :)  Do you have any major holidays in November in Russia?

To answer your question, the use of past perfect is expected in scientific writing.

In my opinion, it is the best tense to use when describing scientific research.  Many different factors and events come into play during research, and the ability to be specific in regards to ordering past actions is needed for clarity.  Plus the entire paper must be written in the same tense - so sometimes it may not be needed except to maintain continuity.

Take this part of the scientific text: By day 10, Betaproteobacteria were the most abundant group, while the abundance of Gammaproteobacteria HAD DECREASED to less than 5%.

If it were written, "By day 10, Betaproteobacteria were the most abundant group, while the abundance of Gammaproteobacteria decreased to less than 5%..." there would be two different tenses in the sentence.  The clause, "by day 10," implies that while something happened at day 10, something happened before day 10 and something may happen after day 10 (requiring past perfect tense).  

Also, scientific writing should stay neutral with all actions being equal.  This is what makes scientific reading so dry and boring to some people.  When I read, "By day 10, Betaproteobacteria were the most abundant group, while the abundance of Gammaproteobacteria decreased to less than 5%..." my mind is drawn straight to "decreased" because it shows more action than the Beta bacteria simply being abundant. "Had decreased" sounds much less action-packed and keeps the sentence reading smoothly.

I'm afraid I'm not doing a good job of explaining myself here.  I hope this helps answer your question.

English as a Second Language

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